\ 

1 1 



UNIVERSITY OF MISSOURI 



A Study Of 
Some Factors Influencing Fruitfulness 

in Apples 

CLEO CLAUDE WIGGANS, B.S. Agr., A.M. 



SUBMITTED IN PARTIAL FULFILMENT OF THE 

REQUIREMENT FOR THE DEGREE OF 

DOCTOR OF PHILOSOPHY 



UNIVERSITY OF MISSOURI 
COLUMBIA 

1918 



UNIVERSITY OF MISSOURI 



A Study Of 
Some Factors Influencing Fruitfulness 

in Apples 

CLEO CLAUDE WIGGANS, B.S. Agr., A.M. 



SUBMITTED IN PARTIAL FULFILMENT OF THE 

REQUIREMENT FOR THE DEGREE OF 

DOCTOR OF PHILOSOPHY 



UNIVERSITY OF MISSOURI 

COLUMBIA 

1918 



UNIVERSITY OF MISSOURI 



&,*& 



COLLEGE OF AGRICULTURE 



#9* 

Agricultural Experiment Station 



BOARD OF CONTROL 

THE CURATORS OF THE UNIVERSITY OF MISSOURI 

EXECUTIVE BOARD OF THE UNIVERSITY 



SAM SPARROW, Chairman, 
Kansas City 



C. B. ROLLINS, 
Columbia 



JOHN H. BRADLEY, 
Kennett 



ADVISORY COUNCIL 
THE MISSOURI STATE BOARD OF AGRICULTURE 



OFFICERS OF THE STATION 

A. ROSS HILL, PH. D., LL. D., PRESIDENT OF THE UNIVERSITY 

F. B. MUMFORD, M. S., DIRECTOR 

STATION STAFF 



AGRICULTURAL CHEMISTRY 
C. R. Moulton, Ph. D. 
L. D. Haigh, Ph. D. 
L. S. Palmer, Ph. D. 
W. S. Ritchie, A. M. 
S. B. Siiirkey, B. S. in Agr. 

C. E. Mangels, 1 M. S. 
T. H. Hopper, 1 M. S. 
V. F. Payne, 1 A. B. 

Mrs. Mary Cochrane Farris, B. S. in Agr. 

AGRICULTURAL ENGINEERING 
E. H. Lehmann, B. S. in A. E. 

ANIMAL HUSBANDRY 

E. A. Trowbridge, B. S. A. 

F. B. Mumford, M. S. 
H. O. Allison, M. S. 

L. A. Weaver, B. S. in Agr. 

D. J. Griswold, A. M. 

BOTANY 
George M. Reed, Ph. D. 
Helen Joiiann, A. M. 

DAIRY HUSBANDRY 
C. H. Eckles, M. S., D. Sc. 
W. B. Combs, A. M. 
W. W. Svvett, A. M. 
M. H. Fohrman, B. S. in Agr. 
Percy Werner, Jr., 1 A. M. , 

ENTOMOLOGY 
Leonard Haseman, Ph. D. V 

K. C. Sullivan, A. M. 

FARM CROPS 
W. C. Etheridge, Ph. D. 

E. M. McDonald, B. S. 
C. A. Helm, A. M. 

J. B. Smith, 1 A. M. 
L. J. Stadler, A. M. 



FARM MANAGEMENT 
O. R. Johnson, 1 A. M. 
R. M. Green, B. S. in Agr. 
FORESTRY 
Frederick Dunlap, F. E. 

E. C. Pegg, M. F. 

HORTICULTURE 
V. R. Gardner, M. S. A. 
H. F. Major, B. S. A. 
J. T. Rosa, Jr., M. £. H. 
H. G. Swartwout, B. S. in Agr. 

POULTRY HUSBANDRY 
H. L. Kempster, B. S. 
G. W. Hervey, 1 B. S. 

SOILS 
M. F. Miller, M. S. A. 
R. R. Hudleson, 1 A. M. 
W. A. Albrecht, M. S. 

F. L. Dwley, A. M. 

H. H. Krusekopf, A. M. 
Wm. DeYoung, B. S. in Agr. 

VETERINARY SCIENCE 
J. W. Connoway, D. V. M., M. D. 
L. S. Backus, D. V. M. 
O. S. Crisler, D. V. M. 
•A. J. Durant, 1 A. M. 
•H. G. Newman, B. S. in Agr. 

OTHER OFFICERS 
R. B. Price, M. S., Treasurer 
J. G. Babb, A. M., Secretary 
E. H. Hughes, A. M., Asst. to Dean 
O. W. Weaver, B. S., Agricultural Editor 
George Reeder, Director Weather Bureau 
Rachel Holmes, 2 A. B., Seed Testing Lab- 
oratory 
J. F. Barham, Photographer 



2 In U. S. Military Service. 

2 In service of U. S. Department of Agriculture. 

(2) 

P a of D. 
DEC 5 |< 



SOME FACTORS FAVORING OR OPPOSING 
FRUITFULNESS IN APPLES* 

The Effect of Certain Conditions and Practices on the 

Development and Performance of the 

Individual Fruit Spur 

C. C. Wiggans 

INTRODUCTION 

It is a generally observed fact that certain varieties of apples 
tend to bear crops in alternate years, while others produce annual 
yields. Some varieties are light bearers but others yield heavy crops. 
In some cases the same variety, or even the same tree, shows great 
variation in its performance from year to year. The principles un- 
derlying these variations in behavior are of scientific interest as well 
as of great importance to practical fruit growers. Horticultural lit- 
erature contains numerous references to the biennial crops of the 
Baldwin in the New England and New York fruit growing sections. 
Among the varieties grown in Missouri, the Ben Davis, Gano, In- 
gram, and York show marked alternation of crops, while the Jona- 
than, Winesap, Grimes, and Missouri generally may be depended up- 
on to give satisfactory crops each year. 

The investigator in considering the factors influencing fruitful- 
ness in apples, must, first of all, give his attention to a study of the 
principles underlying fruit bud formation, for the flower must, of 
course, precede the fruit. Many and varied have been the opinions 
of investigators as to the factors causing flower production. The 
argument has sometimes been advanced that the blooming power is 
inherited, while some writers have maintained the view that flowers 
are dependent upon the presence of a certain specific "blossom 
building" substance. The latter view has been especially noticeable 
among German investigators. Environmental factors such as light, 
heat, accident, etc., have been considered the all important ones in 
some cases, while in others, the effects of certain cultural practices 
have been used as a basis for the explanation of the phenomenon. 
Seemingly, the problem has been of as much interest to plant phys- 
iologists and morphologists, as to the practical growers themselves. 

*Also presented to the Graduate School of the University of Missouri, June, 1918, as 
a thesis in partial fulfillment of the requirements for the degree of Doctor of Philosophy. 

ACKNOWLEDGMENT. The writer wishes to acknowledge his indebtedness to the 
following named men who assisted him to plan and carry out this investigation: Dr. J. C. 
Whitten, Dr. G. M. Reed, Dr. P. F. Trowbridge, and Mr. H. G. Swartwout. 

(3) 



4 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 

It has long been recognized by those interested in plant life that 
in every plant there are two seemingly antagonistic forces, one of 
which is striving to preserve the individual plant, and the other, to 
perpetuate the species. The first of these activities expresses itself 
in the formation of purely vegetative parts, such as stems, roots and 
leaves, thru which the life of the individual may be lengthened, while 
the latter has to do with the formation and maturation of seeds in 
greater or smaller numbers by which the species may be carried 
over from one generation to the next. The former may be spoken 
of as vegetative activity and the latter as reproductive activity, or, in 
the case of fruit trees, as wood growth and fruit growth. 

Vegetative activity always precedes reproductive development 
and, so long as it proceeds with undiminished vigor, few or no blos- 
soms will be formed. With our tree fruits the period of vegetative 
activity may be several years in length while with certain annual 
plants it may be a matter of only a few weeks. In any case, how- 
ever, the maximum vegetative period passes before heavy reproduc- 
tion begins. Maintaining the vigor of the wood growth serves very 
materially to delay the formation of fruits, while, on the other hand, 
a heavy fruit crop tends to decrease greatly the vegetative growth. 
From these general observations, the obvious conclusion has been 
reached that it is impossible to have the greatest efficiency in both 
wood and fruit growth simultaneously in a single individual. A 
plant, then, cannot be of the highest degree of service to itself and 
to its species at one and the same time. 

Apple trees during the first few years of their life produce few 
or no blossoms. The energies of the plant are directed to the forma- 
tion of a framework of branches upon which the later crops of fruit 
are to be borne. Finally, however, the bearing age is reached but 
this is found to differ very materially in the different varieties and 
even in the same variety when grown under different cultural and 
soil conditions. From this time until its death, the tree remains a 
potential fruit bearing organization. The amount of fruit borne, 
however, often shows a very striking variation, ranging from a very 
light crop to a very heavy one. This phenomenon is sometimes 
spoken of as alternation. 

Alternation, referring primarily to the bearing of heavy and 
light crops in alternate seasons, seems to be more or less a varietal 
characteristic. With certain varieties regular crops are expected, 
while with others a heavy crop is almost invariably followed by a 
light one. This habit of alternation also seems to be much more 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 5 

characteristic of our later commercial varieties than of some of the 
older sorts grown in the orchards of the early settlers. This may 
have come about because of the emphasis that is now placed upon 
high yields. In the earlier days, when markets were limited, regular 
crops were more desirable than heavy crops. 

In an investigation of the factors influencing fruitfulness in ap- 
ples, so many avenues of research are open that it is folly to attempt 
to take all of them into consideration in a single investigation which 
must be more or less limited to certain lines. Previously, nearly all 
investigators have been inclined to consider the problem from the 
standpoint of the entire tree, or, of the entire orchard, in its rela- 
tion to a specific treatment or factor. In this study, however, the 
main idea centers around the factors and conditions influencing the 
behavior of an individual fruit spur. Since the tree is composed of 
numerous individual fruiting parts, the factors influencing the indi- 
vidual spur must ultimately have a proportionate influence upon the 
entire organization. Hence an attempt has been made to keep con- 
stantly in mind the fruiting parts as individuals rather than in mass, 
and the greater part of the work has been done with the individual 
fruit spurs. 

Moreover, for the purpose of this study, it is generally assumed 
that a blossoming spur is also a fruiting spur. Under field condi- 
tions, however, some flower clusters may fail to set fruit, but the 
fact still remains that a spur developing a blossom is a potential 
fruiting spur for the following year, and it is here so considered. 

LITERATURE 

A critical review of the literature bearing upon the factors favor- 
ing or opposing fruitfulness in apples reveals the fact that many ex- 
planations have been offered for the variations found in the fruiting 
habit of an apple tree. It is quite noticeable that many of these ex- 
planations are based upon general observations and conclusions 
rather than upon actual scientific data, and especially is this true in 
the older writings. Definitely planned experimental work is virtu- 
ally confined to the last twenty-five years, and dates approximately 
from the time the agricultural experiment stations became well estab- 
lished in research work. 

Not all writers have been interested directly in the production 
of an increased number of blossoms for some have been concerned 
with the reserve materials which are always found to be present in 
woody plants. The amount and nature of these reserves vary accord- 



6 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 

ing to the season and character of the part under consideration, and 
these variations have sometimes been used as a basis to explain the 
phenomena observed. Thus, are recorded not only the observations 
of horticulturists but those of biologists and chemists as well. 

The natural evolutionary development of the apple during the 
centuries that it has been under cultivation, has very likely had con- 
siderable influence upon the cultural practices of the succeeding 
periods. Therefore, it seems but natural to suppose that the manage- 
ment suitable for the apple as it was first known would be not at all 
applicable to the modern commercial high yielding varieties. Also, 
an increasing knowledge of plant structure and function, in all proba- 
bility, has been productive of improved methods of fruit growing. 
All recommendations, however, based upon either general observa- 
tions or actual knowledge, have for their purpose an increase in the 
yield or an improvement in the character of the fruits borne. 

One point upon which the majority of writers are in perfect 
accord is, that fruit bud formation is dependent upon a supply of re- 
serve food material. With the better understanding of the sap flow 
in plants, this idea has become more and more prominent. Even the 
early writers seemed to appreciate that there is some connection be- 
tween the food supply and the sap, and hence they devised methods 
by which they thought they could modify the sap and thereby also 
influence the food supply. Particular methods were evolved for the 
various parts of the plant and changes in the character of the food 
supply, etc., were also suggested. 

Since many of the writers have considered the effects of several 
methods or treatments upon fruitfulness, it seemed advisable to con- 
sider the literature in chronological order rather than by topics. This 
plan has been used in the following review: 

One of the earliest records found of an interest being taken in 
the factors influencing fruitfulness is the statement of Lonicerus 
(1587) quoted by Zacharias 152 *. This early writer seems to have 
reached the conclusion that an excess of nourishment leads to a 
very marked extension of the vegetative branches, but that no fruit 
will be borne under these conditions. This same doctrine, that great 
vegetative growth is not compatible with great reproductive activity, 
can be subscribed to today. 

According to Noehden 104 , Van Oosten, (1711) the Dutch botan- 
ist, stated that a "moderate sap flow," secured by frequent trans- 
planting or by summer pruning, will result in fruit production. While 

*Sce bibliography for this and subsequent number references thruout. 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 7 

he probably possessed very little knowledge concerning the sap flow, 
yet this writer suggested two methods which will encourage fruitful- 
ness and these methods are even now sometimes used for this pur- 
pose. 

The beneficial effects of ringing were observed by De la Baisse 
(1753), Bonnet (1754) and Duhamel (1758). These reports were 
recorded by Mobius". Duhamel apparently seems also to have had 
some knowledge of the effects of pruning. 

Knight 78 early in the nineteenth century published many papers 
dealing with horticultural subjects. Among his observations, Knight 
made note of the increased fruitfulness of horizontal branches as 
compared with upright ones. He explained this by the assumption 
that the decreased sap movement in the horizontal branches was the 
direct cause of their greater fruitfulness. He suspected that the 
heavy fruit crops borne immediately following a warm bright season 
when only a few fruits were matured, was due to the fact that the 
sap had not been expended in maturing an excessive crop. In some 
of his earlier papers he leaned to the belief that the bearing age of a 
tree is dependent to a large extent upon hereditary factors, but later, 
ringing is mentioned as a way of increasing fruitfulness, this being 
due to the accumulation of descending" sap. Knight really had a 
much better knowledge of plant physiology than his predecessors and 
hence was enabled to give a more nearly correct interpretation of 
his results. It is interesting to note the close agreement between some 
of his ideas and those of the present day. 

Forsyth 46 in a textbook on the general subject of fruit growing 
published in 1802 made the following statement, "Never shorten the 

young branches except they are very thin nor prune any of 

the young shoots the second year, as many of the eyes, almost at the 
end of the shoot, will, if it be strong, become fruit buds next year." 
Evidently, this writer had been making some very accurate observa- 
tions upon the method of fruit spur formation. 

That fruit bud formation may be stimulated by checking or di- 
minishing the growth was the opinion of Noehden 104 (1818). Ring- 
ing was suggested as one means of accomplishing this end. 

Prince lls (1830) believed that the amount of available moisture 
had a marked effect upon the fruitfulness of grapes. 

Philips 112 (1831) declared that, "Pruning is to be avoided as 
much as possible as it creates useless branches and prevents the 
fruiting." Cole 28 (1849) mentioned the following factors as being 
conducive to fruitfulness and early bearing; root pruning, ringing, 



8 MISSOURI AGK. EXP. STA. RESEARCH BULLETIN 32 

bending down the branches, transplanting, use of certain stocks, short- 
ening-in, and change of soil or climate. He stated also that certain 
varieties are regular bearers while others bear only in alternate years. 
However, he did not agree with the opinions expressed by others 
that this alternation is due to exhaustion and points out, in support 
of his contention, that certain kinds produce annual crops. In his 
opinion, the bearing year in alternating varieties may be changed by 
removing all of the blossoms during the heavy bearing year. 

Barry 13 (1851), after observing that fruit buds originate as leaf 
buds, the differentiation taking place during the latter part of the 
growing season, finally stated that the immediate causes of fruit bud 
formation are not satisfactorily understood. He quoted Dubreuil, 
however, as being of the opinion that fruit buds are dependent upon 
stored plant food and that their formation is brought about if the cir- 
culation of sap is obstructed. This obstruction causes a slowing up 
of the sap movement so that the sap is more thoroly elaborated, and 
hence, becomes better adapted to fruit bud formation. Lindley 83 
(1852) believed that plants must attain a certain age before flowers 
will be formed, and that this age may be influenced materially by 
the nutrition of the tree. He further stated that fruit bud formation 
is probably due to an accumulation of plant food. 

Field 41 (1859) recommended breaking, pinching, and twisting 
the branches as methods of inducing fruitfulness in the pear. He 
believed also that a large quantity of fibrous roots is essential for 
fruit production and hence root pruning may be practiced. Down- 
ing 36 (1864) agreed with Field that root pruning may be useful but he 
assigned an entirely different reason for it. By lessening the root 
system an overabundance of plant food is made available for the 
branches and this material then forms fruit buds. In the opinion of 
this writer, heavy crops exhaust the tree and thus cause alternation. 
However, this habit may be overcome by thinning while the apples 
are small. He also recommended that the soil be kept in "high 
condition." 

Rivers 121 (1866) was a very strong advocate of root pruning, 
especially for dwarf trees, as a remedy for barrenness. He supposed 
that trees could be kept fruitful only by preventing the formation of 
large roots since these go downward and imbibe crude sap which 
causes great twig growth and few or no fruits. 

Warder 143 (1867) summed up his observations by stating that 
fruit bud formation is due to the accumulation within the tree of 
nutritive materials, and the exhaustion of the soil of wood-forming 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 9 

elements. From the time the tree reaches maturity, then, the bear- 
ing habit is regulated by the balance between the materials which 
produce wood and those that produce fruit. Young trees need sum- 
mer pruning to check their vigor and cause laterals to develop while 
older trees require dormant pruning to thin the fruit and to renew 
the vigor. Thus, it is seen that in the young trees, vegetative vigor 
must be restrained and fruit production encouraged, while in the 
aged trees, the exact opposite is the case. 

For twenty-five years following the publication of Warder's 
"American Pomology" very few papers appeared dealing with the 
fruitfulness of apples. Seemingly, the writers of this period were 
content to let the question stand without additional comment. How- 
ever, about 1880 there began to appear frequent articles concerning 
the chemical nature of the stored plant reserves. Halsted 61 (1890) 
pointed out the importance of reserves to trees and also made some 
descriptions of the various storage tissues. Fie found but little ap- 
parent difference between leaf buds and fruit buds so far as sugar 
storage was concerned. However, he pointed out that leaf buds store 
up much more starch than the others on account of the fruit buds 
having to supply the developing fruit with this material. In his 
opinion flower buds are not terminal but rather simply overshadow 
the terminal leaf bud which is down among the blossoms. Fischer 43 

(1891) also called attention to the importance of reserves, and of 
their activities before any exterior growth takes place. 

Maynard 97 (1888) concluded from some girdling experiments 
with crabapple trees that girdling will cause the production of an 
abnormal number of blossom buds but that it is an unsafe stimulus 
to use. Taft 135 (1891) gave root pruning as one cause of fruitful- 
ness, but stated that this practice is not to be recommended. Quinn 119 

(1892) said that summer pruning causes a change in the flow of sap 
from the ends of the branches which results in fruit formation. 
Gurney 60 (1894) assigned exhaustion as a cause of alternation but 
said, "Bearing only in alternate years can in a large measure be 
broken up by a careful system of feeding or fertilizing." 

Sorauer 130 (1895) has given this problem considerable attention, 
mainly from the physiological point of view. He maintained that 
under certain conditions, controllable to some extent by man, buds 
may be changed from one form to another. He said in part: 

"Plants will only develop flowering buds when the food material formed 
in the leaves is copiously stored up in the stem and branches as reserve ma- 
terial, and not when this material is immediately used up in the production of 
new vegetative organs. 



10 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 

"Of our apple trees it is a well known fact that in warm insular climates 
they grow into magnificent foliage trees but remain unproductive of fruit. 

"That a diminution of the supply of water accompanies the production of 
flowers in nature may be gathered from the fact that most trees and shrubs 
produce their flowers on short reduced branches or spurs. The comparison 
of the anatomical structure of such a short shoot with that of a long leafy 
shoot confirms our statement, too, that an increase in stored food material is 
necessary for the production of flowers. The former shoots have by far 
more storage tissue than the latter 

"The withholding of water in such a treatment prevents the use of 
assimilated plant substance for the growth of new shoots and causes it to be 
stored up near the buds. 

"For the production of flowering buds it is essential to decrease the sup- 
ply of water and of nitrogenous salts, to increase the phosphates supplied 
to the plants and to increase the illumination." 

Sorauer also discussed to some extent the effects of pruning 
upon fruitfulness and suggested that bending, twisting, notching, 
ringing, and peeling may be used to make pruning even more effec- 
tive. 

Klebs 76 (1890-1905) published several papers upon subjects re- 
lating to the reproduction of plants. His earlier investigations were 
carried out with algae and fungi because of their simplicity and 
rapidity of development, and also because the external conditions 
could be so easily and at the same time absolutely controlled. From 
the lower forms, however, he progressed to the use of the higher 
species and his later experiments were with phanerogams. This 
writer, in particular, emphasized the fact that the environment of a 
plant plays a most important role in the rate and kind of develop- 
ment made by it and its various parts. He showed that a plant may 
remain vegetative indefinitely if placed under the proper conditions. 
On the other hand, when the vegetative growth is inhibited reproduc- 
tion at once begins. These changes in the character of the growth 
may be brought about entirely by a change in external conditions. 

Work with the lower plants convinced Klebs that reproduction 
is affected by the amount and intensity of light, heat, moisture, and 
food supply, while the later experiments led him to believe that 
higher plants reacted in precisely the same way. Plants pass from 
the vegetative to the flowering state with changes in their external 
conditions and, at the same time, interior changes resulting in greater 
storage of plant food may also be taking place. Flowers, however, 
are not the result of an absolute amount of nourishment but rather 
of the relation between the decomposition and recomposition of these 
substances. In support of this opinion, he pointed out the fact that 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 11 

badly nourished plants always blossom early. Intense light and low 
humidity are favorable to flower production and the intensity of 
nutrition also has great significance in this connection. Lessening 
the food supply results in flower production, provided the plant 
possesses reserves. This is the condition brought about by ringing. 
Whether external conditions are to exert a favorable or unfavorable 
influence upon reproduction depends altogether upon the effect 
which they have upon internal conditions. 

Other investigators coming after Klebs and Sorauer have sub- 
mitted additional proof that there is a definite relation between the 
food supply and the character of plant development. External con- 
ditions favoring flower growth always oppose extensive twig and 
leaf development. External conditions favoring great availability of 
plant food always result in vigorous vegetative growth. Climatic 
conditions may have quite an influence in this respect. This was 
very forcibly brought out by Balmer 10 (1896) in describing the dif- 
ference in the fruiting habits of the same variety when planted under 
different conditions. In a region where rainfall is abundant, exces- 
sive vegetative growth is noticed, while in a section where the rain- 
fall is much less, even the young trees tend to overbear. This, of 
course, means that much more attention must be given to pruning 
and other orchard operations under those conditions. 

During the more recent years a considerable literature has been 
developed in connection with the effects of such orchard operations 
as pruning, fertilization, cultivation, spraying, ringing, etc., and along 
with this, some general observations with regard to the fruiting habit. 

Schweitzer 127 (1898) commenting upon the results secured from 
the ash analysis of twigs from apple trees said, "surely the much 
larger absolute amount of lime, phosphoric acid and potash in the 
bearing twigs must be either the cause or the condition of their bear- 
ing." 

Bailey 7 (1898) enumerated several factors that may cause bar- 
renness in apple trees but finally stated that in the nature of the 
tree there is no reason why it should not fruit more or less continu- 
ously. Later 8 (1911) this same author concluded that the side bud 
on a bearing spur does not receive sufficient nourishment to develop 
into a fruit bud and, even tho the blossoms may be removed, it still 
may not produce a fruit bud for the following year. Waldron 142 
(1899) mentioned an "inherited tendency" to produce flower shoots 
as being a very potent cause of fruitfulness. 

Q Q ££5i 52 53 (1899-1901) in making studies of blossom formation 
in our common tree fruits showed that environmental factors have 



12 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 

great influence upon the early development of the bud. He con- 
cluded that fruit buds are due to nutrition rather than structure since 
a spur may bloom at one, two, or three years of age, or it may 
never bloom, and also because of the fact that a spur may bloom 
and even fruit two years in succession. Alternation is not due to 
exhaustion since a weakened or exhausted tree always produces a 
large number of blossoms. Very favorable conditions for fruit bud 
formation result in such great development of these buds during 
that season that no spurs remain for the development of buds for 
the succeeding crop. He 55 also said (1916) "a water supply insuffi- 
cient for rapid growth may suffice for abundant fruit bud forma- 
tion," and then called attention to the fact that fruit buds are usually 
formed during the drier part of the year. 

Daniel 32 (1900) declared that from the physiological standpoint 
there is little or no difference in the effects of girdling and grafting. 

Experimental evidence submitted by Brown and Escombe 20 
(1902) indicates that the amount of carbon dioxide in the air has 
a very marked effect upon flower formation. 

Thomas 137 (1902) called attention to the fact that some varieties 
fruit more abundantly on the younger wood than do other sorts. He 
also stated that summer pruning hastens the formation of fruit 
spurs near the base of the pruned twig much more than dormant 
pruning. 

Speaking with reference to thinning, Beach 16 (1903) said, 
"thinning the fruit does not appear to cause any material change in 
either the amount or regularity of the fruit production." 

Sablon 123 (1903) reported that the reserves in the twigs of a 
pear grafted upon a quince root are greater than those of a tree 
growing upon its own roots, thus tending to make it more fruitful. 
Later 125 (1906) he made further studies upon the reserves of trees 
and found that the great variation in the kind and amount of these 
reserves was dependent upon the season and the part under considera- 
tion. 

Loew 85 (1905) combated the idea of earlier German writers that 
there is a specific blossom building material when he stated that 
blossoms are the result of a certain concentration of sugars. Fischer 4 * 
(1905) agreed with Loew that there is no special blossom forming 
substance. He also stated that girdling, instead of causing starvation 
of the parts above the girdle, results in an accumulation of plant re- 
serves thereby causing greater blossom production. 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 13 

Flowers and flower bud formation require a relatively high 
illumination according to Clark 27 (1905), a fact which is supported 
by Paddock's 108 (1905) account of the greater and earlier fruitful- 
ness of trees in the increased sunshine of high altitudes. 

Chandler 24 (1905) presented the idea that alternation is due 
more to the formation of the blossom than to the later development 
of the fruit and for this reason thinning is not effective in overcom- 
ing the alternating habit. He also stated that the bearing habit can 
be controlled by pruning only in case the pruning dates from the 
early development of the tree. Herrick 67 (1910) reached the con- 
clusion that systematic thinning should have some influence toward 
annual cropping, thereby doing away with the "off years" of cer- 
tain varieties. 

According to Ikeda 71 (1910) the Japanese fruit growers have 
always felt that alternation is due to nature and can not be controlled 
in any way. He then told of the pruning which is done by breaking 
off the bearing twigs at the time the fruit is harvested. 

Waugh 144 (1910) reached the conclusion that if a tree is starved, 
it will make no new growth, the spurs will deteriorate, and the crops 
become scant, while too much wood growth will take place at the 
expense of the spurs and fruit. 

Manaresi and Tonegutti 93 95 (1910) found that fruit-bearing 
wood is much richer in nutrients than foliage-bearing parts, and also 
that there are material differences in the size and shape of the leaves 
on the bearing and non-bearing spurs. 

Although Newell 102 (1910) stated that a single bud naturally 
cannot produce two crops in succession, yet, according to this author, 
the tree can be kept bearing annually. He expressed the opinion 
that the fruit bud receives no sap until the needs of the end of the 
branch have been fully satisfied. 

Stewart 132 (1910) said, "the off year may be frequently largely 
overcome by fertilization and other care," and later 133 (1917), recom- 
mended for maintaining high and uniform yields, first, the prevention 
of large crops by thinning, second, an ample supply of food and 
moisture, and third, the avoidance of injury to the roots thru culti- 
vation, etc. 

Pickett 113 (1911) reported that while fertilization had little or 
no effect upon the number of fruit buds, cultivation with or with- 
out a cover crop always showed an increase. A proper balance, 
easily destroyed by too much pruning, or other treatment, between 
the working area of the foliage and the food supply, is necessary to 



14 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 

insure a full and regular supply of fruit buds in apple orchard 114 

(1913). 

Paddock and Whipple 110 (1911) observed that varieties which 
frequently form fruit buds upon the one year wood are more likely 
to be annual bearers than varieties which fruit only on the older 
parts. The alternation of individual spurs is, in their estimation, due 
to a depletion of their energies by the fruit during the bearing year. 

Dry weather at the time of fruit bud formation always makes a 
good prospect for the next year's crop, according to Macoun 88 (1912). 

Batchelor 14 (1913) thought that the spur needs a year to recover 
its exhausted energies after fruiting, and hence, a light crop is borne 
in alternate years. Newsham 103 (1913) agreed with this statement 
and then added that removing the blossoms or young fruit tends to 
cause annual crops. This writer also stated that checking the growth, 
while inducing fruit fulness, does not maintain it. 

Magnien 92 (1913) recommended basic slag as a fertilizer for 
apples because it leads to abundant fruit bud production. According 
to Remy 120 (1913), blossom formation is not affected by high 
amounts of phosphorus, potash, or lime, but a certain amount of 
nitrogen seems to be necessary. 

Howe 69 (1914) said that ringing, while sometimes effective in 
inducing or increasing fruitfulness, is an unsafe stimulus to apply 
to fruit trees. 

Gourley 57 (1914) reported that practically all methods of tillage 
treatment resulted in yields superior to those secured from the sod 
plots. In making a detailed study of the fruit spurs, this author 58 
(1915) found that the spur having a fruit bud upon it possessed a 
greater supply of starch than one without a fruit bud. The leaf area 
of a spur is always greater during the non-bearing year. Thinning 
experiments with the Baldwin did not give appreciable results so far 
as the regular bearing of the tree was concerned. 

Sears 128 (1914) agreed with Thomas 138 (1914) that rank growth 
is always opposed to fruitfulness since an abundance of plant food 
is essential to blossom formation. He further stated that the effect 
of summer pruning is not well understood — it depends upon the time, 
nature, and extent of the treatment, — but Drinkard 38 (1915) and 
Batchelor and Goodspeed 15 (1915) recommended summer pruning as 
a means of stimulating fruitfulness. 

Alderman and Auchter 3 4 (1916-17) in a series of experiments 
in West Virginia came to the general conclusion that heavy dormant 
pruning on young trees delays the bearing age while lighter pruning 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 15 

hastens it. In the case of old trees, however, vigorous pruning 
stimulates fruit production. They found that corrective dormant 
pruning was more effective in stimulating fruitfulness than summer 
pruning. Auchter 6 (1917) states "thinning does not influence subse- 
quent crops nor cause trees naturally biennial in bearing habit to bear 
each year." 

From the work of Lewis 81 (1915), Gardner 47 (1915), Kraus 79 
(1915), Magness 8991 (1916), Bradford 18 (1915), and Yeager 151 (1916) 
of the Oregon agricultural experiment station, the following general 
conclusions may be drawn : A large percentage of the spurs bear 
only once in two years. Varieties fruiting on the newer parts are 
more regular bearers than those which fruit on the older portions. 
The condition of the tree as a whole determines whether a spur will 
fruit two years in succession. There is a correlation between the size 
of a spur and its productiveness but the floriferousness of a spur 
lessens as the spur becomes older. Fruit bud formation is due to a 
fair amount of adjacent leaf surface since the plant foods are stored 
up near the point of synthesis, a state of affairs making each twig 
more or less independent of the remainder of the tree. The greatest 
effects of pruning are manifested near the pruning cut. Summer 
pruning stimulates fruit bud formation near the base of the pruned 
twig only, and not thruout the body of the tree where the fruit spurs 
have already become well established. 

Winkler 148 (1916) concluded that under conditions favorable to 
enzyme action, vegetative growth predominates, while conditions in- 
hibiting enzyme activity are favorable to reproductive activity. An 
accumulation of carbohydrates is given as one condition bringing 
about the cessation of enzyme action. 

According to Pickering 115 (1916) it is unproven that fruiting is 
due to a gradual accumulation of the plant reserves which become 
exhausted thru the production of a heavy crop. He concludes that 
the great variation found in the size of crops borne over a series of 
years is due to atmospheric conditions more than to any other factor 
even tho there is a tendency to alternation in certain varieties. 

Retardation of growth always results in an increase in the starch 
proportion of the parts above ground, — at least, these are the results 
reported by Hartwell 64 (1916) after working with the potato. 

Barker and Lees 12 (1916) reported that different degrees of dor- 
mant pruning result in practically an equal number of fruit buds be- 
ing formed but that these buds are differently distributed on the tree. 

Heinicke 66 (1917) stated that a dry sunny season is favorable 
for fruit bud production. He also found that bearing spurs are 



16 



M 



ISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 



always heavier in weight than non-bearing spurs and that the great- 
est leaf area is found on the spurs with the greatest amount of con- 
necting tissue. The age of the spur from two to four or five years 
apparently has little effect on its fruitfulness. 

The established habit of the tree is far more influential upon the 
fruitfulness than the kind or extent of the pruning, according to 
Kains 73 (1917). Twig and small branch pruning, however, tend both 
to thin the fruit and favor regular annual bearing. 

Butler 22 (1917) said that the theory that alternation is due to ex- 
haustion has little or no foundation, but that it is a natural phe- 
nomenon to be predicated from the mode of flowering. Flower bud 
development, no matter on what kind of a branch, always occurs 
where six to eight sessile leaves have developed in a single period of 
vegetation. A slow, quick maturing, sessile growth, due to a scant 
but sufficient moisture supply, coupled with a vigorous photosyn- 
thetic activity is responsible for flower bud development. In his 
opinion small yearly departures from the mean growth will result in 
a more uniform production. 

GENERAL STATEMENT OF THE PROBLEM 

The apple yield of the entire United States shows a wide varia- 
tion from year to year as the following table will indicate. 



Table 1. — Annual Production of Apples in U. S* 



Year 


Yield 
Barrels 


Year 


Yield 
Barrels 


1909 


48,707,000 
47,213,000 
71,340,000 
78,407,000 


1913 


48,470,000 


1910 _ 


1914 


84,400,000 


1911 


1915 


76,670,000 


1912 


1916 


67,415,000 








♦Yearbook, U. S. D. A., 


1916, p. 635. 









The foregoing variation is probably to be expected when it is 
considered that allowances must be made for the wide ranges of 
both soil and climate over which the apple is grown in this country, 
and also because of the increased plantings. Unfavorable conditions 
in any one section are likely to be balanced by favorable ones in an- 
other, and so, on the whole, the foregoing figures do not represent 
the actual variation in yield which may be expected in any particular 
section. 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 



17 



When the Missouri yield alone is considered even a greater 
variation than that shown in Table 1 is found. This smaller area 
represents more nearly uniform conditions and hence indicates the 
degree of difference which is often found in apple yields. 

Table 2. — Annual Production of Apples in Missouri* 



Year 


Yield 
Barrels 


Year 


Yield 
Barrels 


1889 

1890 


2,899,000 
2,420,000 
3,220,000 
1,381,000 

936,000 
2,569,000 
4,816,000 
3,780,000 
3,599,000 

784,000 
2,165,000 
2,767,000 
3,500,000 
3,900,000 


1903 


2,067,000 


1904 


3,233,000 


1891 


1905 

1906 


2,100,000 




6,667,000 




1907 


433,000 




1908 


2,033,000 


1895 

1896 


1909 

1910 


3,323,000 
2,533,000 


1897 


1911 


3,867,000 


1898 


1912 


6,400,000 


1899 


1913 


2,633,000 


1900 


1914 


4,167,000 


1901 


1915 


6,287,000 


1902 : 


1916 


2,700,000 



•Missouri Bureau of Labor Statistics Report 37, 1915, p. 286. 
**Yearbook U. S. D. A. 1916, p. 635. 

An examination of the foregoing table reveals the interesting 
fact that, as a rule, the heavy yield occurred every third year. For 
instance, the years 1915, 1912, 1909, and 1906, all showing heavy 
yields, are invariably followed by a relatively light crop which in 
turn is followed by a medium yield which, apparently, leads up to 
the heavy production again. The same is shown to some extent for 
the earlier years also, but here such regularity can hardly be ex- 
pected since during the period 1889 to 1899 very extensive plantings 
were being made and each year in that period showed a correspond- 
ingly greater number of trees in bearing. Such a state of affairs 
would naturally interfere with the regular sequence of bearing. How- 
ever, the yields for the later years, which probably are more accurate 
than the others, represent the production of a more uniform num- 
ber of trees and consequently may be considered as more representa- 
tive of the way in which trees normally bear. 

From the foregoing it is evident that the question of fruitfulness 
in apples is a very important one to the fruit grower who demands 
regular annual crops in order that his business may be a stable one. 

A search of the literature previous to the initiation of this pro- 
ject revealed the fact that no particular attention had ever been 



Ig MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 

given to a study of the individual fruit spurs. Previous investigators 
have based their opinions with respect to spur behavior, largely upon 
general observations and conclusions. Casual observations made by 
fruit growers generally have indicated that there is probably a corre- 
lation between the previous performance of a spur and its later fruit- 
fulness, but data either confirming or contradicting this view have 
not been recorded. 

In the light of the above facts, when this investigation was be- 
gun in 1913, it seemed advisable to center the attention upon the in- 
dividual fruiting branches rather than to consider the performance 
of the tree or orchard as a whole. It seemed only logical to look in 
this direction for an answer to the question, Is the alternation of a 
Gano tree due to the inability of the individual spur to blossom 
and fruit two years in succession, or to some other factor, or factors? 
The question also arises as to whether the regular bearing of the 
Jonathan is caused by the fact that only a relatively small proportion 
of the spurs blossom any one season. Here again an answer must be 
sought by examining the fruit spurs and not by casual observation 
of the entire tree. 

While the general object of this investigation has been to de- 
termine the effect of certain conditions and practices upon the de- 
velopment and performance of the individual fruit spur or branch, 
the following specific objects may be mentioned : 

1. To determine whether an individual spur or branch blossoms 
two or more years in succession, in alternate years, or only once in 
its life history as a fruiting part. 

2. To determine whether there is a correlation between the 
concentration of plant sap and stored reserves in bearing and non- 
bearing parts, and the observed bearing or non-bearing condition. 

3. To correlate the leaf area of a spur with the fruiting habit 
that it possesses. 

4. To observe the exact effect of girdling upon the concentra- 
tion of sap in various parts of the trees. 

5. To determine the effect of fertilizers upon dwarf trees 
planted in pots. 

6. To record the osmotic strength of sap from different parts 
of trees grown under different systems of tillage. 

7. To note the effect of certain systems of pruning upon the 
formation and development of the fruiting parts. 

8. To note the effect of etherization upon the fruiting parts of 
young trees. 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 19 

SPUR PERFORMANCE RECORDS 

In order to determine accurately the exact behavior of the indi- 
vidual spurs, it is essential to keep performance records of the spurs 
over a series of years. Accordingly, in the fall of 1913 a suitable 
label was attached to each spur that had produced a fruit that year. 
(Fig. 1.) This labeling was carried out systematically upon one 
tree each of the Jonathan, Gano and Rome varieties. These trees 
were located on the Horticultural Grounds of the Missouri Experi- 
ment Station. They were approximately eighteen years old and ap- 
parently in full health and vigor. 

In the spring of 1914, labels were attached to all of the blossom- 
ing spurs on the same trees, these labels being so marked that they 
could be distinguished from those attached the previous season. At 
the end of the season still another distinguishing mark was made up- 
on the labels attached to the fruiting spurs. These marks were so 
made that by an examination of the label it was possible to determine 
the exact behavior of that spur during the past year. The results 
of the first year's observations are: 

Variety Gano 

Number of spurs fruiting in 1913 598 

Number of same spurs blooming in 1914. . 49 
Percentage 8.2 

These data show distinctly that only a very small percentage of 
the spurs which fruit one season will even blossom the next year. 
However, there is shown a considerable difference in the behavior 
of the spurs upon the different varieties. Thus, it will be seen in 
the case of the Jonathan, the ability to blossom in the season imme- 
diately following the one in which a fruit is matured, is shown in 
nearly twice as great a proportion as in either the Rome or Gano. 
(The greater number of fruits on the Gano tree was probably due, 
at least to some degree, to the fact that it was a larger tree than 
either of the others.) 

From these observations as a starting point the work was con- 
tinued during the seasons of 1915, 1916, and 1917, so that in all this 
report covers a period of five years' work. Labels were attached 
to blossoming and fruiting spurs during these seasons so that at 
the end of the period it was possible to tell exactly how each spur 
had behaved each season since the observations were begun. The 
variety list was also extended so as to include Winesap, Grimes, and 
York, thus giving three varieties which are more or less regular 



Rome 


Jonathan 


223 


228 


19 


36 


8.5 


15.8 



20 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 

bearers and three that exhibit alternation under ordinary conditions. 
Some later observations were also made upon fourteen-year-old trees 
of various varieties growing in the famous loess soil along the Mis- 
souri River. 

Obviously, it would be almost impossible to record the perform- 
ance of every spur upon every tree under observation. Hence, in 
the following figures no attempt has been made to include all of 
them. In each case, however, the number taken has been large 
enough to preclude accidental variation, and since they were taken 
from various parts of the tree so as to include all the different con- 
ditions found on the tree, they may be taken as being representative 
of the tree as a whole. 

In Tables 3 to 13 inclusive, an attempt has been made to syste- 
matize the blossoming records secured on the above trees. These 
tables represent really the summary of still longer tables, and in order 
to simplify them, no account has been taken of the spurs which both 
blossom and fruit in distinction to those which blossom only. Since 
only a limited number of combinations are possible for each spur's 
performance during the five-year period, the spurs showing the same 
sequence of blooming and non-blooming have been grouped together. 
New spurs are, of course, being added to the tree each year, so it 
must be remembered that the following records represent the be- 
havior of the present spur system of the tree and not the system 
that was on the tree five years ago when the investigation began. 
Many of the spurs which were fruiting at that time have now de- 
veloped into larger branches upon which other fruit spurs are borne. 

In the tables, the first five columns contain a record of the be- 
havior of the spur during the past five years, while the right-hand 
column indicates the number of spurs exhibiting that particular com- 
bination. The letter "B" represents in each case a blossom cluster 
for that particular season, while a blank indicates that no blooms 
were shown. It might be noted that the record for the year 1913 
indicates, in the main, only those spurs which fruited that season 
altho an attempt was made to include all of those that blossomed. 
However, since it was sometimes quite difficult to be sure upon this 
point this explanation is given. The last line in each table represents 
the percentage of blossom*, out of the total number, which blossomed 
in the given years. 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 



21 



Table 3. — Performance Record of Indi- 
vidual Spurs From a Jonathan 
Tree Grown in Clay Loam Soil 



Table 4. — Performance Record of Indi- 
vidual Spurs From a Jonathan 
Tree Grown in Loess Soil 













No.of 


1913 


1914 


1915 


1916 


1917 


Spurs 










B 


333 








B 


B 


86 






B 


B 


B 


41 




B 


B 


B 


B 


3 




B 




B 


B 


59 


B 






B 


B 


2 






B 




B 


238 




B 


B 




B 


21 


B 


B 


B 




B 


2 


B 




B 




B 


97 




B 






B 


66 


B 


B 






B 


1 


B 






B 


B 


3 

137 




--, 


B 


B 




47 




B 


B 


B 




11 


B 




B 


B 


... 


5 




B 




B 




101 


B 




B 


B 




2 
61 




B 


B 






S 


B 


B 


B 






9 

15 


B 










1 


9.0% 


21.1% 


40.1% 


37.3% 


70.7% 


1346 













No.of 


1913 


1914 


1915 


1916 


1917 


Spurs 










B 


134 








B 


B 


92 






B 


B 


B 


20 




B 


B 


B 


B 


1 


B 


B 


B 


B 


B 


1 


B 




B 


B 


B 


3 




B 




B 


B 


12 


B 






B 


B 


2 






B 




B 


51 


B 




B 




B 


9 




B 






B 


2 









B 




155 






B 


B 




10 




B 


B 


B 




1 


B 




B 


B 




1 




B 




B 




44 


B 


B 


B 


B 




1 
15 


B 


B 


B 






2 
1 


3.4$ 


11.0% 


20.4% 


61.6% 


58.7% 


557 



Table 5. — Performance Record of Indi- 
vidual Spurs From a Grimes Tree 
Grown in Clay Loam Soil 



Table 6. — Performance Records of Indi- 
vidual Spurs From a Winesap Tree 
in Clay Loam Soil 













No.of 












No.of 


1913 


1914 


1915 


1916 


1917 


Spurs 


1913 


1914 


1915 


1916 


1917 


Spurs 










B 


250 










B 


188 








B 


B 


21 








B 


B 


110 






B 


B 


B 


9 






B 


B 


B 


70 




B 


B 


B 


B 


1 




B 


B 


B 


B 


9 




B 




B 


B 


5 


B 




B 


B 


B 


19 






B 




B 


185 




B 




B 


B 


76 


B 




B 




B 


42 


B 






B 


B 


1 




B 






B 


2 






B 




B 


64 


B 


B 






B 


2 




B 


B 




B 


1 


B 




B 


B 
B 


B 


2 

110 

17 


B 


B 


B 


B 


B 
B 


6 

1 

49 




B 


B 


B 




1 






B 


B 




11 




B 


B 


B 




12 

197 


B 


B 


B 


B 
B 




3 
34 




B 


B 






12 






B 






11 


B 


B 


B 






25 
3 


B 


B 


B 
B 






2 
3 


B 










5 




B 








3 


8.3% 


4.4% 


42.7% 


17.2% 


57.0% 


901 


4.1% 


19.5% > 


30.1% 


56.1% 


82.4% 


661 



22 



MISSOURI AGR. EXP. ST A. RESEARCH BULLETIN 32 



Table 7. — Performance Records of Indi- 
vidual Spurs From a Winesap Tree 
Grown in Loess Soil 



Table 8. — Performance Records of Indi- 
vidual Spurs From a Rome Trek 
Grown in Clay Loam Soil 













No.of 


1913 


1914 


1915 


1916 


1917 


Spurs 










B 


102 








B 


B 


56 






B 


B 


B 


21 




B 


B 


B 


B 


8 


B 




B 


B 


B 


5 




B 




B 


B 


14 


B 


B 




B 


B 


5 






B 




B 


27 




B 


B 




B 


9 


B 




B 




B 


7 




B 




B 


B 


3 

34 






B 


B 




10 




B 


B 


B 




4 


B 




B 


B 




1 




B 




B 




6 


B 


B 


B 


B 




2 
1 


6.0% 


16.1% 


28.8% 


55.8% 


81.6% 


315 













No.of 


1913 


1914 


1915 


1916 


1917 


Spurs 










B 


3 






B 


B 


B 


1 

428 






B 


B 




48 




B 


B 


B 




4 


B 




B 


B 




2 




B 




B 




313 


B 


B 




B 




2 


B 




B 


B 




1 
95 




B 


B 






4 


B 


B 


B 






13 

5 


1.9% 


35.7% 


18.1% 


86.8% 


0.3% 


919 



Table 9. — Performance Records of Indi- 
vidual Spurs From a York Tree 
Grown in Clay Loam Soil 



1913 



6.3% 











No.of 


1914 


1915 


1916 


1917 


Spurs 








B 


81 






B 


B 


2 




B 


B 


B 


1 


B 




B 


B 


3 




B 




B 


48 


B 


B 




B 


1 




B 


B 


B 
B 


23 

7 

11 




B 


B 




4 




B 






8 




B 






1 


2.1% 


45.2% 


11.2% 


87.3% 


190 



Table 10. — Perf6rmance Records of In- 
dividual Spurs From a York Tree 
Grown in Loess Soil 















No.of 


1913 


1914 


1915 


1916 


1917 


Spurs 










B 


47 








B 


B 


5 






B 




B 


4 


B 




B 




B 


1 


B 








B 


1 








B 






180 






B 


B 






31 




B 


B 


B 






2 


B 


B 


B 
B 


B 
B 






1 

22 


B 


B 
B 


B 

B 
B 


B 
B 






4 

5 

17 

1 


B 


B 


B 








1 
3 


B 


B 










1 


2.7% 


3.9% 


25.7% 


76.7% 


14 


7% 


326 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 



23 



Table 11. — Performance Records of In- 
dividual Spurs From a Gako Tree 
Grown in Clay Loam Soil 













No.of 


1913 


1914 


1915 


1916 


1917 


Spurs 










B 


7 






B 


B 


B 


1 

1047 






B 


B 




8 




B 


B 


B 




4 


B 




B 


B 




2 




B 




B 




545 


B 




B 


B 




26 

47 




B 


B 






1 


B 


B 


B 






6 
130 


B 


B 








3 


B 










37 


3.9% 


36.4% 


3.6% 


87.1% 


0.5% 


1864 



Table 12. — Performance Records of Ik- 
dividual Spurs From a Gano Tree 
(No. 1) Grown in Loess Soil 













No.of 


1913 


1914 


1915 


1916 


1917 


Spurs 










B 


2 








B 


B 


4 




B 




B 
B 


B 


2 
159 






B 


B 




1 


B 


B 


B 


B 
B 




1 
43 


B 


B 
B 


B 


B 




1 
1 


B 


B 


B 






3 
1 


2.3% 


20.9% 


2.6% 


97.2% 


3.6% 


218 



Table 13. — Performance Records of In- 
dividual Spurs From a Gano Tree 
(No. 2) Grown in Loess Soil* 













No.of 


1913 


1914 


1915 


1916 


1917 


Spurs 










B 


22 








B 


B 


51 




B 




B 


B 


35 


B 






B 


B 


1 






B 




B 


6 


B 




B 




B 


1 




B 




B 


B 


4 
83 






B 


B 




8 


B 




B 


B 




1 




B 




B 




15 


B 


B 




B 




1 


B 




B 


B 




1 
1 


2.1% 


23.9% 


7.4% 


85.2% 


52.1% 


230 



*Blossoms practically all destroyed in 
1916 by spray solution. (See page 24 
for further explanation). 



An examination of the preceding tables shows that the varieties 
studied may be divided roughly into two classes, one of which pro- 
duces a fair supply of blossoms each year but with no exceedingly 
productive seasons, while the other exhibits a very high percentage 
of blossoms one season and a comparatively low one the next. Jona- 



24 



MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 



than, Winesap, and Grimes belong to the former, and Rome, York, 
and Gano to the latter group. The varieties of the first group are 
usually considered as annual bearers, while the others show rather 
marked alternation. 

The difference in the behavior of these two groups is brought 
out more clearly in Table 14, which is a summary of the preceding 
tables. 



Table 14. — Percentage of Fruit Spurs Biossoming in the Various Seasons. 

(1913-1917) 

(Summary of Tables 3 to 13.) 



Variety 



Jonathan 

Jonathan 

Grimes 

Winesap 

Winesap 

Rome 

York .... 

York .... 

Gano ... 

Gano 

Gano 



No. 1 
No. 2* 



Soil 
Type 
Where 
Grown 


Total 
No. 
of 
Spurs 


Percentage Distributi 


on of Bl 


jssoms 


1913 


1914 


1915 


1916 


1917 


Clay Loam 


1346 


9.0 


21.1 


40.1 


37.3 


70.7 


Loess 


557 


3.4 


11.3 


20.4 


61.6 


58.7 


Clay Loam 


901 


8.3 


4.4 


42.7 


17.2 


57.0 


Clay Loam 


661 


4.1 


19.5 


30.1 


56.1 


82.4 


Loess 


315 


6.0 


16.1 


28.8 


55.8 


81.6 


Clay Loam 


919 


1.9 


35.7 


18.1 


86.8 


0.3 


Clay Loam 


190 


16.3 


2.1 


45.2 


11.2 


87.3 


Loess 


326 


2.7 


3.9 


25.7 


76.7 


14.7 


Clay Loam 


1864 


3.9 


36.4 


3.6 


87.1 


0.5 


Loess 


218 


2.3 


20.9 


2.6 


97.2 


3.6 


Loess 


230 


2.1 


23.9 


7.4 


85.2 


52.1 



*Blossoms practically all destroyed in 1916 by spray solution. 

It will be noted that the behavior in 1917 of the spurs on the 
tree, Gano No. 2, is in apparent contradiction to that of Gano No. 1. 
This may be explained by the fact that in 1916, at which time both 
trees had a heavy bloom, the spraying operations were so delayed 
that it was necessary to spray tree No. 2 when it was in full blos- 
som. As a result, only a very small percentage of the blossoms set 
fruit, hence the spurs were able to mature fruit buds for the fol- 
lowing year. That they did so, is evidenced by the amount of blos- 
som carried by the tree in 1917. It is thus seen, notwithstanding the 
statements of some investigators to the contrary, that the bearing 
year may be changed, and, to this extent, is subject to the control of 
the horticulturist. 

Attention is also called to the fact that the York tree growing 
in loess soil, produces its blossoms in the season alternating with the 
heavy fruit crop of the tree in the clay loam soil. Even in the 
same orchard this same variation in behavior is sometimes found. 
In each case, however, marked alternation is shown. It gives strength 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 



25 



to the statement sometimes made that when alternation is once estab- 
lished, there is a great likelihood that it will be continued thru the 
following years, unless interrupted by accident or design. 

Outside of the foregoing exceptions the varieties show very 
great similarity in their behavior in the different soil types. This is 
at least suggestive of the conclusion that after all the soil condi- 
tions do not affect markedly the behavior of the individual spurs 
with respect to their individual alternation. 

With the idea of showing a little more clearly the behavior of 
the individual spurs, Tables 15 and 16 have been prepared. The 
first table indicates the percentage of the spurs now on the tree, 
which have produced blossom buds in successive seasons, while the 
second table shows the percentage of spurs which have blossomed in 
alternate years. 

Table 15. — Percentage of Spurs Blossoming in Alternate Seasons 



Variety 



Soil 
Type 
Where 
Grown 


Total 
No. 
of 
Spurs 


Clay Loam 


1346 


Loess 


557 


Clay Loam 


901 


Clay Loam 
Loess 


661 
315 


Clay Loam 
Clay Loam 
Loess 


919 
190 
326 


Clay Loam 
Loess 


1864 

218 


Loess 


230 



Percentage Blooming in 



1913-15 



1914-16 



1915-17 



Total Per- 
centage 
Showing 
Alternation 



Jonathan 
Jonathan 
Grimes 
Winesap 
Winesap 
Rome ... 
York ... 
York .... 
Gano 
Gano Ni 
Gano Ni 



0.6 
0.3 
2.7 
0.4 
0.0 
1.4 
0.0 
0.0 
0.2 
1.4 
0.0 



7.6 

8.0 

1.3 

5.1 

2.5 

34.2 

0.0 

1.5 

28.7 

20.1 

7.4 



26.6 

10.7 

21.8 

10.9 

13.6 

0.1 

37.9 

1.5 

0.0 

0.0 

3.0 



34.8 
19.0 
25.8 
16.4 
16.1 
35.7 
37.9 
3.0 
28.9 
21.5 
10.4 



*Blossoms practically all destroyed in 1916 by spray solution. 

Table 16. — Percentage of Spurs Blossoming in Successive Seasons 



Variety 



Soil 
Type 
Where 
Grown 


Total 
No. 
of 
Spurs 


Clay Loam 


1346 


Loess 


557 


Clay Loam 


901 


Clay Loam 


661 


Loess 


315 


Clay Loam 


919 


Clay Loam 


190 


Loess 


326 


Clay Loam 


1864 


Loess 


218 


Loess 


230 



Percentage Blooming in 



1914-15 



1915-16 



1916-17 



Total Per- 
centage 
Showing 

Succession 



Jonathan 

Jonathan 

Grimes 

Winesap 

Winesap 

Rome 

York 

York 

Gano 

Gano No. 1 
Gano No. 2* 



0.3 
0.0 
1.3 
0.3 
0.0 
0.3 
0.0 
0.3 
0.0 
2.7 
37.8 



4.6 
2.1 
1.9 
2.1 
4.7 
5.8 
2.1 
18.3 
0.8 
0.9 
2.9 



14.1 

23.5 

3.9 

43.1 

31.4 

0.0 

3.1 

1.5 

0.0 

0.4 

0.0 



19.0 

25.6 

7.1 

45.5 

36.1 

6.1 

6.2 

20.1 

0.8 

4.0 

40.7 



'Blossoms practically all destroyed in 1916 by spray solution. 



26 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 

From Table 15 it will be noted that there are relatively slight 
differences between the different varieties in regard to the percent- 
ile Jonathan tree, a regular bearer, has as great a percentage of 
age of spurs which alternate in their blooming habit; in other words, 
spurs which bloom only once in two years as the Gano, which is 
notorious as an alternate cropper. When trees grown on similar 
soils are compared, the difference is very slight, the only exception 
occurring in the case of the Winesap. The Winesap is really one 
of our most reliable regular annual bearers and an explanation for 
this may rest in the fact that only a small percentage of the spurs 
do alternate in their blooming habit. Gano No. 2 also shows a slight 
variation from the average as do also the York and Jonathan grown 
upon loess soil. This is perhaps to be expected since these trees as 
yet have hardly attained a fully established bearing age. 

Table 16 exhibits by no means such close agreement of varieties 
as that noted for the preceding one but rather the varieties are again 
divided into two general groups. With the apparent exception of 
the Grimes, the varieties producing regular crops possess to a marked 
degree the ability to produce a blossom on the same spur two years 
in succession. This ability is exhibited to a higher degree in the 
Winesap than in the Jonathan, a performance which might be ex- 
pected because of the small percentage of Winesap spurs which show 
alternation. 

Examination of the performance records of the second group of 
varieties shows that only a very small proportion of the spurs are 
able to produce successive crops of blooms. The York grown in 
loess soil is seemingly an exception, as is also Gano No. 2. The lat- 
ter case, however, is fully explained by the fact that the 1916 crop 
of blossoms was practically destroyed, and hence, the tree was able 
to mature a larger number than normal in 1917. In the case of 
the York, it may be said that local environmental conditions, as well 
as the younger age of the tree, probably played a very important part. 

The fact brought out just above, which is that spurs on varieties 
which bear regularly are able to produce blossoms two years in suc- 
cession in a high percentage of cases while alternate bearers are not, 
suggests an explanation for the figures recorded in Table 14. The 
regularity of the blossom in the case of the first group is conceiv- 
ably due to the fact that a great many of the spurs are able to pro- 
duce blossoms two years in succession. Also, the inability of the 
second group of varieties to blossom two years in succession coupled 
with their exceedingly heavy production of blossoms one year will 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 



27 



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28 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 

account for the small number of blooming spurs during the fol- 
lowing season. Thus, the difference between alternating and non- 
alternating varieties seems to be due to the ability of spurs on the 
regular bearing sorts to blossom two years in succession. 

While recording the performance record of the spurs, an attempt 
was also made to approximate their age by counting the number of 
scale scar rings upon the spur. In some instances the age given is 
simply an estimate. This is especially the case with the old spurs 
because after the age of six or seven is reached, it becomes difficult 
to be absolutely positive as to just how old the spur may be. Table 
17 will serve to show the relative ages of the blossoming spurs on 
the various varieties. 

It is of interest to observe that by far the greater part of the 
blossoming spurs in every case are between three and seven years of 
age. This holds true for both alternating and regular bearing sorts 
and hence leads to the conclusion that the age at which the spur 
begins to bear is of little significance in relation to the bearing 
habit of the variety. 

Because of the youthfulness of a large part of the spurs, it is 
again noted that by far the greater part of the spurs present on the 
trees when these observations were begun are spurs no longer. 
They have developed into branches and many new spurs have been 
formed. A spur seems to be at its highest state of efficiency when 
from three to six or seven years of age. 

THE FOOD RESERVES OF FRUIT SPURS 

The amount of available plant food has long been considered as the 
determining factor in fruit bud formation but there seems to be very 
little evidence or actual data to support this view. It then has 
seemed worth while to compare as far as possible the plant food re- 
serves of fruiting and non- fruiting spurs and their various parts, that 
is, their leaves and fruits. 

There are two general methods by which the relative amounts 
of stored food in plant tissue may be determined, the first, by de- 
termining the concentration of the plant sap thru the use of the 
freezing point method, and the second, by making an actual chemical 
analysis of the parts under consideration. The former method was 
used extensively by both Chandler 25 and Winkler 148 at this Station, 
while the English investigators, Davis and Daisch 33 employed the 
latter in the determination of plant carbohydrates. In the first 
method, it is not possible to calculate the absolute amount of materials 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 29 

present, only the relative proportions are indicated. Neither can the 
amount of starch be determined by this method. Through the use 
of the analytical method, however, both the identity and absolute 
amounts of the substances present can be determined if suitable 
methods are employed. Both methods have been used in this investi- 
gation, but, in either case, only for the determination of the relative 
amounts of the reserves rather than their absolute percentages. 

1. Depression of the freezing point. — The sap for the de- 
termination of the freezing point depression was secured by grinding 
up the parts under consideration by means of a food chopper and 
then subjecting the ground material to considerable pressure. The 
material was enclosed in muslin before being placed in the pressing 
blocks. These blocks were of hardwood and so made that one of 
them just fit into a cavity in the side of the other. A jackscrew 
served as a means by which the pressure was applied. Figure 2 
shows the various details of the press. The expressed sap was col- 
lected into a test-tube thru a small funnel. 

After being expressed the sap was kept in a cool place until its 
freezing point could be determined. An ordinary Beckman ther- 
mometer was used and the low temperature secured thru the use of a 
salt and ice mixture. A small amount of sap was placed in a test 
tube, the amount being just sufficient to cover the bulb of the ther- 
mometer. The thermometer was then inserted and the tube plunged 
into the salt and ice. It was usually found to be advisable not to 
have this tube in direct contact with the ice because the cooling in 
that case was too rapid. Best results were secured by first insert- 
ing into the freezing mixture a tube slightly larger than the one con- 
taining the sap, and then placing the latter inside the former. An 
air jacket then surrounds the tube containing the sap and the ther- 
mometer. This will slightly retard the cooling and thus insure a 
more uniform cooling. 

The depressions given in the following tables represent the dif- 
ference between the freezing point of distilled water and the freez- 
ing point of the particular sap. The plant saps, being of a higher 
concentration, freeze at a lower temperature. The greater this con- 
centration, the lower will be the freezing point, and hence, the greater 
the depression. It is assumed that the saps with the greater depres- 
sion possess the greater supply of plant food. No attempt has been 
made to calculate the osmotic strength of the various saps but this 
could be very easily done by reference to the osmotic strength tables 
worked out by Harris and Gortner 62 63 . 



30 



MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 



Table 18 indicates the depressions which were found in the 
spur sap from spurs bearing or non-bearing in the years specified. 
In every case, an attempt was made to get spurs representative of 
these two conditions, the spurs being taken from the same branch 
as far as possible. Only the short fruiting branches were used, 
rarely were they more than three inches long. So far as outward 
appearance was concerned, the only difference between the two sets 
of spurs was that one group had fruited in the year specified and 
the other had not. After the spur material was ground, the sap was 
expressed as previously described. 

Table 18. — Depression of Jonathan Fruit Spur Sap 



Date 



Bearing 
previous 
year 


Non-bearing 

previous 

year 


Bearing 

same 
year 


Non-bearing 

same 

year 


Degrees C. 
2.450 


Degrees C. 
2.300 
1.730 
1.990 
2.170 


Degrees C. 


Degrees C. 


2 100 






2 120 






2 370 








1.865 
1.860 
1.200 
1.200 
1.060 
1.225 
1.010 
1.250 
1.500 
1.205 
1.995 


1.855 


2.130 
1.200 


2.000 
1.340 


2.000 
1.200 
1.330 






1.070 


1.355 


1.340 


1.530 
1.110 


1.265 
1.285 
1.080 
1.290 


1.210 
1.215 
1.040 
0.910 


1.400 
1.370 
1.435 
1.945 



February 6, 1915 

February 27, 1915... 

March 19, 1915* 

April 4, 1915* 

June 8, 1915 

June 21, 1916 

July 6, 1916 

July 15, 1915* 

July 17, 1915 

July 22, 1916 

July 31, 1915 

August 1, 1916 

August 17, 1916 

September 15, 1916. 
October 14, 1916 



'Spurs from trees grown in loess soil. 



A study of the figures in Table 18 shows that during a consid- 
erable portion of the year the sap from the bearing spurs and also 
sap from spurs fruiting during the preceding season, has a greater 
depression than sap from corresponding nonfruiting parts. This dif- 
ference may not be large enough to be of special significance. It 
gives no conclusive proof to the claim that in a non- fruiting year the 
spur is accumulating reserves for the next year's crop of buds. 
However, it may be possible that the greater part of the reserves 
are stored farther back from the end of the branch. Then, too, 
these data do not include a measure of the reserves which are stored 
up as starch. 

The accompanying chart shows graphically the depressions re- 
corded in Table 18. It is noticed that the sap of non-fruiting spurs 
is slightly more concentrated than the sap of a spur holding a fruit 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 



31 



at that particular time. On the other hand, sap from spurs bearing 
the year previous to the determination shows consistently a greater 
concentration than the sap from corresponding parts that did not 
fruit during the preceding season. This difference gradually disap- 
pears, however, and apparently both kinds of spurs reach a similar 
degree of concentration about July 1. 




Depression of Jonathan spur sap 

Marked seasonal variations in the sap density are also observed. 
The greatest change comes in late June and early July, at which time 
there is a sudden drop in concentration. This is the season at which 
the fruit buds for the next year's crop are forming and this abrupt 
drop may be either the cause or an effect of this fruit bud formation. 
It is noticeable in both the bearing and non-bearing spurs. 

Apparently there is little difference in the concentration of the 
spur sap which can be attributed directly to soil conditions. Spurs 
from trees grown in two widely varying soil types showed little 
variation in the depression of the sap. Also, altho all of the above 
determinations were made upon sap from a Jonathan tree, there 
seems to be little varietal variation in this respect as the later de- 
terminations show. 

The observations noted above concerning the difference in sap 
density in fruiting and non-fruiting parts at once opens up the ques- 
tion as to whether this condition may not be due to a withdrawal of 



32 



M 



ISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 



moisture from the spur by the ripening fruit or by the leaves — a de- 
ficiency which may not be altogether overcome by the following 
spring. Chandler 25 has observed that toward the ripening period 
water may be drawn from the fruit to the leaves. There may also 
be a similar movement of moisture from the spur which would at 
once have its effect upon the concentration of the sap of the spur. 

The above determinations are perhaps too meager to warrant 
any positive conclusions but they are given as being suggestive of 
the idea that perhaps after all the food supply is not so important 
as has been assumed by some writers. 

Leaf sap taken from leaves on fruiting and non-fruiting spurs 
did not show so consistent a difference as sap from the spurs them- 
selves. The variations in these depressions, as shown in Table 19 
are so great that it seems unwise to suggest any possible explanation. 

Table 19. — Depression of Leaf Sap From Bearing and Non-bearing 
Jonathan Fruit Spurs 



Date ■> 


Fruiting Condition 


Bearing 
1915 


Non-bearing 
1915 


Bearing 

1916 


Non-bearing 
1916 


June 21, 1916 


Degrees C. 
2.680 
1.510 
1.970 
1.605 
2.340 
2.255 
1.995 


Degrees C. 
2.690 
1.590 
1.980 
1.890 
2.205 
1.995 
1.945 


Degrees C. 

2.550 


Degrees C. 

2.880 


Tuly 15, 1915 




July 22, 1916 


2.035 
1.510 
2.540 
2.190 
2.260 


2.015 


August 1, 1916 


2.100 


August 17, 1916 


2.290 


September 15, 1916 


2.460 


October 14, 1916 


2 110 







Table 20. — Depression of Spur Sap from Spurs Bearing 3, 2, 1, or no Fruits 



Date 


Variety 




Fruiting Condition 




3 fruits 


2 fruits 


1 fruit 


no fruit 


June 8, 1915 
June 21, 1916 .... 
July 6, 1916 
July 15, 1915 
July 17, 1915 
July 17, 1915 


Jonathan 

Woodmansee 

Woodmansee 

Jonathan* 

Jonathan 

York* 

Woodmansee 

Jonathan 

Woodmansee 

Woodmansee 

Woodmansee 


Degrees C. 
1.905 
2.060 

1.250 


Degrees C. 
1.860 
2.040 
1.340 
1.130 
0.950 
1.200 
1.310 
0.920 
1.295 
1.535 
1.450 


Degrees C. 
1.865 

2.010 
1.160 
1.200 
1.060 
1.130 
1.225 
1.010 
1.510 
1.500 
1.205 


Degrees C. 
1.855 




1.330 




1.070 




1.300 


July 22, 1916 


1.365 




July 31, 1916 
August 1, 1916.... 


1.100 


1.270 
1.600 
1.360 




July 17, 1916.... 




September 15, 1916 









'Spurs from trees grown in loess soil. 




Fig. 1. — Gano apple tree on which some of the labeling work was done 




Fig. 2. — Press and blocks by means of which the plant saps were expressed 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 



33 



Also figures on the depression of spur sap, leaf sap, and fruit 
sap from spurs bearing three, two, and one fruits, are so inconsist- 
ent as to be of no assistance in helping to explain fruitfulness or non- 
fruitfulness. In general, it may be stated that it apparently makes 
little or no difference upon the concentration of the sap as to how 
many fruits a spur is maturing. The seasonal differences in the de- 
pression of the fruit spur sap are again brought out by Table 20 
which checks very well with Table 18 in this respect. 



Table 21. — Depression of Leaf Sap from Spurs Bearing 3, 2, or 1 Fruits 



Date 


Variety 


Fruiting Condition 


3 fruits 2 fruits 


1 fruit 


June 21, 1916 


Woodmansee 

Woodmansee 

Jonathan 

Woodmansee 

Woodmansee 

Woodmansee 

Woodmansee 


Degrees C. 
2.660 
1.930 

1.940 
1.895 
2.650 


Degrees C. 
2.610 

1.790 
1.510 
1.830 
1.870 
7. ^n 


Degrees C. 
2 580 


July 6, 1916 


1 830 


July 15, 1915 


1 510 


July 22, 1916 

August 1, 1916 


2.035 
2.135 


August 17, 1916 


2 540 


September 15, 1916 


2.640 2.045 


2 190 











Table 22. — Depression of Fruit Sap from Spurs Bearing 3, 2, or 1 Fruits 



Date 


Variety 


Fruiting Condition 


3 fruits 


2 fruits 1 fruit 


June 8, 1915 


Jonathan 

Woodmansee 

Woodmansee 

Woodmansee 

Woodmansee 

Woodmansee 

Woodmansee 


Degrees C. 

1.000 
1.880 
1.180 
1.325 
1.325 
1.395 
1.415 


Degrees C. 
.960 
2.040 
1.040 
1.345 
1.330 
1.440 
1.435 


Degrees C. 
950 


June 21, 1916 

July 6, 1916 

July 22, 1916 


1.900 
1.040 
1 290 


August 1, 1916 


1 320 


August 17, 1916 


1 320 


September 15, 1916 


1 355 







2. Chemical Determinations. — In order to get at the problem 
from a different angle and to compare especially the relative amounts 
of sugars and starch in the spurs, it was decided to employ some 
simple chemical methods. The method used in the sugar analysis 
was adapted very largely from the work of Davis and Daish 33 and 
the starch determination was made in accordance with the directions 
in standard works on agricultural analysis. While these determina- 
tions possibly may not be all that might be desired from the chemical 
point of view, they are at least comparative and it is this connection 
that they are of value here. 



34 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 

Considerable difficulty was encountered in securing satisfactory 
results, and, altho the work was begun early in 1917, several 
months had passed before it was felt that results of any reliability 
were obtained. The results given below were secured from spur ma- 
terial only, since the buds alone or the leaves could not be used satis- 
factorily. 

The analyses were carried out according to the following plan: 

1. Grind the material with a food chopper and then weigh out a 15- 
gram sample. 

2. Boil the sample for one hour in 500 cc. of 95 per cent alcohol to 
which had been added 5 cc. of ammonium hydroxide. 

3. Filter and wash the residue with alcohol. Preserve the filtrate for 
the sugar determinations. Dry the residue for the starch determination. 

4. Add 2 cc. of toluene to the filtrate and evaporate down to 40-50 cc. 
at 70° C. Dilute to 250 cc. with water. 

5. Precipitate the tannins in 200 cc. with basic lead acetate (sp. gr. 1.25), 
adding a small excess of this material. Make up to 250 cc. and filter. 

6. To 200 cc. of this filtrate, add enough solid sodium carbonate to re- 
move the excess basic lead acetate. Again make up to 250 cc. and filter. 

7. To 25 cc. of this filtrate add a small amount of Fehling's Solution, 
boil for two minutes and then filter. Dry and weigh the cuprous oxide precip- 
itate. This gives a measure of the amount of reducing sugar present. 

8. To another 25 cc. sample add enough sulphuric acid to make it faintly 
acid to methyl orange. Then add 10 per cent by weight of citric acid crys- 
tals. Boil for ten minutes and then neutralize to phenolphthalein with sodium 
hydroxide. Add a sufficient quantity of Fehling's Solution to precipitate the 
total sugars as cuprous oxide. Filter, dry and weigh the precipitate. 

9. Two and one-half grams of the residue from procedure No. 3 are 
placed in a flask with 200 cc. of water and 20 cc. of hydrochloric acid (sp. 
gr. 1.125). It is then boiled in a reflux condenser for two and one-half 
hours. One cc. of toluene is added after it cools. 

10. Nearly neutralize with sodium hydroxide, using phenolphthalein as 
an indicator. Dilute to 250 cc. 

11. Add Fehling's Solution to 25 cc, boil for two minutes, then dry and 
weigh the cuprous oxide precipitate. This indicates the amount of starch 
present. Pentoses and pentosans are also included. 

The results secured are given in Table 23. No attempt has been 
made to calculate the actual percentage of sugars or starch present. 
The figures represent only the weight of cuprous oxide present in the 
aliquots indicated. All determinations were made upon the spurs of 
a Yellow Transparent tree. This variety was selected because of the 
accuracy with which the past performance of the spurs could be 
determined. 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 35 

Table 23. — Sugar and Starch Content of Yellow Transparent Fruit Spues 



Date of Determination 


Condition 
of Spur 


Weight of Cuprous Oxide Representing 


Reducing 
Sugar 


T»tal 

Sugar 


Starch 


October 22, 1917 


Bearing 

Non-bearing 

Bearing 

Non-bearing 

Bearing 

Non-bearing 

Bearing 

Non-bearing 

Bearing 

Non-bearing 

Bearing 

Non-bearing 

Bearing 

Non-bearing 

Bearing 

Non-bearing 

Bearing 

Non-bearing 

Bearing 

Non-bearing 

Bearing 

Non-bearing 


.0153 

.0191 

.0167 

.0215 

.0720* 

.0150 

.0594 

.0615 

.0305 

.0477 

.0300 

.0384 

.0255 

.0520 

.0335 

.0325 

.0320 

.0400 

.0225 

.0180 

.0170 

.0275 


.0447 
.0502 
.0530 
.0488 
.0760 
.0780 
.0800 
.0690 
.0727 
.0877 
.0700 
.0800 
.0530 
.0965 
.0780 
.0750 
.0855 
.1000 
.0740 
.0500 
.0325 
.0540 


.1861 
.1815 
.1605 


November 17, 1917 


.1730 
.1569 


December 1, 1917 


.1560 
.1336 


December 19, 1917 


.0990 
.1332 


January 3, 1918 


.1477 
.1500 


January 24, 1918 


.1500 
.1395 


February 11, 1918 

March 6, 1918 


.0915 
.1145 
.1325 
.1685 


March 20, 1918 

April 3, 1918 


.1585 
.1355 
.0975 
.1505 




.1505 



*It is very probable that a portion of the non-reducing sugar is also included in this 
determination. 

The number of determinations is small and the series incom- 
plete in that there are no figures available for the important summer 
months preceding and during the time of fruit bud formation. Posi- 
tive conclusions probably should not be formulated but the data are 
at least suggestive. It will be noticed that in a majority of the cases 
there seems to be a slightly greater amount of sugar, both reducing 
and total, in the non-bearing spurs. The starch content of the non- 
bearing spurs, however, does not average quite so high as in the 
bearing spurs but there is considerable variation in these results. The 
amount of starch apparently decreases somewhat, in both kinds of 
spurs, as the growing season approaches, while the amount of sugars 
increases. 

Judging from these few determinations, some emphasis is given 
to the theory that the non-bearing spurs are able to lay up a greater 
amount of reserves than spurs which are maturing fruits. When 
compared with the total amount of reserves, however, this excess is 
very small. These results do not agree altogether with those secured 
from the freezing point determinations. The latter, however, gave a 



36 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 

measure of soluble materials only. If the conclusion reached by 
Magness 89 , that reserves are stored near the point of synthesis, is a 
true one, then it would seem that the non-bearing spur accumulates 
only a slightly greater reserve supply than the fruiting spur. This 
difference, however, may be sufficient to account for the lack of 
fruit bud formation on such a large percentage of bearing branches. 

NUMBER OF LEAVES AND LEAF AREA OF FRUIT SPURS 

General observation long ago led to the conclusion that spurs 
maturing fruits had a smaller leaf area than adjacent spurs having 
no fruit upon them. In order to secure some definite idea as to the 
degree of this difference, some counts and measurements of the 
leaves on fruit spurs have been taken. 

Counts made in 1915 gave the following figures concerning the 
number of leaves on the spurs. Several varieties were used, the 
number of spurs taken being large enough to be representative of the 
tree as a whole. In every case, as will be seen from Table 24, the 
non-bearing spur has the greater number of leaves, when averages 
are taken. 

Table 24. — Number of Leaves on Bearing and Non-bearing Fruit Spurs 





Variety 


Average 
on 


Number of Leaves 
Each Spur 




Bearing 


Non-bearing 




8.70 
7.98 
9.38 
8.32 




8.66 




9.14 




9.85 


Minkler 


8.46 









In the next two seasons further counts and also some measure- 
ments were made, the leaf area being determined by the use of a 
polar planimeter. A summary of these results is given in Table 25. 
These data represent the figures secured from the measurements of 
more than two hundred and fifty spurs and hence may be taken as 
representative. It will be noted that from the average total leaf 
surface of the spur and the average number of leaves, the average 
size of the individual leaf has been calculated. 

To give some idea of the range of variation found in both the 
number of leaves on a single spur and their total area, the figures on 
a few spurs taken at random from Jonathan and Woodmansee trees 
are also given. (Tables 26 and 27.) 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 



37 



Table 25. — Average Number of Leaves and Amount of Leaf Surface on 
Bearing and Non-bearing Spurs 



Variety 



Bearing Spurs 



No of 
Leaves 



Total 
area 



Av. Leaf 
Size 



Non-bearing Spurs 



No of 
Leaves 



Total 
area 



Av. Leaf 
Size 





6.10 
4.36 
6.16 
4.38 
5.38 
5.36 
6.65 


sq. in. 

13.72 

15.67 
9.86 
6.83 

11.25 
6.96 

10.83 


sq. in. 
2.25 
3.59 
1.57 
1.55 
2.08 
1.29 
1.62 


7.40 
5.75 
8.15 
6.16 
6.66 
7.64 
8.41 


sq. in. 
20.80 
21.70 
13.66 
13.67 
15.39 
9.89 
14.58 


sq. in. 

2.81 


Summer Colville 


3.77 
1.67 


Woodmansee .... 
Ben Davis 


2.21 
2.31 
1.29 


Jonathan 


1.73 



Table 26. — Number and Size of Leaves on Bearing and Non-bearing 
Jonathan Fruit Spurs 





Bearing 






Non-bearing 




Spur No. 


No. of 
Leaves 


Total 
Leaf 
Area 


Spur No. 


No. of 
Leaves 


Total 
Leaf 
Area 


1 


7 
7 


sq. in. 

15.76 
9.69 


1 

2 


5 
8 


sq. in 
9.49 


2 


12.30 


$ 


10 


17.53 


3 


6 


10.40 


4 


9 


12.48 


4 _... 


9 


13.34 


5 


5 


8.45 


5 


9 


18.63 


6 


6 


13.19 


6 


11 


28.40 


7 


7 


12.72 


7 


8 


18.64 


8 


14 
2 


20.05 
4.28 


8 


9 
11 


18.01 


9 


9 


18.14 


10 


6 


12.78 


10 


7 


12.15 



Table 27. — Number and Size of Leaves on Bearing and Non-bearing Wood- 
mansee Fruit Spurs 



Bearing 



Spur No. 



1 

2 
3 
4 
S 
6 
7 
8 
9 
10 



No. of 
Leaves 



Total 
Leaf 
Area 



sq. in 
8.40 
5.41 
7.12 
3.82 
6.56 
5.05 
9.41 

11.80 
7.63 
4.73 



Non-bearing 



Spur No. 



1. 
2. 
3 

4. 
5. 
6 
7. 
8 
9. 
10 



No. of 
Leaves 



Total 
Leaf 
Area 



sq. in 
15.05 
11.99 
13.57 
11.22 

9.23 
11.61 

8.80 
21.76 
22.20 
18.04 



38 



MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 



In every case it is shown that non-bearing spurs have a larger 
number of leaves and a greater total leaf surface than non-fruiting 
spurs. When the average size of the individual leaf is computed, 
however, it is found that no very marked difference is present. It 
seems, therefore, that so far as the size of the individual leaf is con- 
cerned, it makes little difference whether it is upon a fruiting or 
non-fruiting spur. The greater total leaf area of the non-bearing 
part apparently comes almost wholly from the increased number of 
leaves which it develops. 

The relative sizes of the individual leaves, and also the total 
leaf area, on bearing and non-bearing spurs is brought out clearly in 
Table 28. To get the figures given in this table, it is necessary only 
to divide the average individual leaf area of the non-bearing spur by 
that of the bearing spur. A similar operation gives the proportion 
between the total leaf area of non-bearing and bearing spurs. 

Table 28. — Proportions Between Non-bearing and Bearing Spurs in Respect 
to ( 1 ) Area of Individual Leaves, and (2) Total Leaf Area of the Spur 





Variety 


Individual 
Leaf Area 


Total Leaf 
Area of Spur 




1.06 
1.00 
1.06 
1.05 
1.11 
1.24 
1.42 


1.35 




1.42 




1.38 




1.38 
1.36 




1.51 




2.00 



With the exception of Woodmansee and Doctor the varietal 
agreement in Table 28 is exceptionally good. Ben Davis also shows 
a slightly higher proportion between the sizes of individual leaves 
from non-bearing and bearing spurs than the more regular cropping 
varieties such as Missouri and Jonathan. There is just a suggestion 
here that this higher proportion may be correlated with alternation, 
for both the Ben Davis and Woodmansee are noted alternate bearers, 
the Woodmansee alternating probably more even than the Ben 
Davis. The other sorts have not fruited sufficiently long in this 
section for their bearing habits to be well known. 

From these measurements, it is made clear that potentially, the 
non-fruiting spur has the much larger leaf surface from which to 
draw its supply of elaborated plant food. If this food is stored near 
the point where elaborated, then the non- fruiting spur should have 
the greater amount of such materials to draw upon in times of 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 



39 



emergency. Reasoning from this alone, it is not difficult to see why- 
fruit buds should form more often on non-fruiting than on fruiting 
spurs. 

EFFECTS OF GIRDLING UPON THE CONCENTRATION 
OF PLANT SAP 

Girdling has often been recommended as a very effective means 
of stimulating fruitfulness. With the purpose in view to determine 
the actual effects of girdling as revealed by the changes brought 
about in the plant sap concentration, some preliminary experiments 
were begun in the spring of 1915. These first tests were conducted 
with nursery trees three years old, since it was thought the results 
obtained would be representative of what might occur on older trees. 
The number of available trees was so small, however, that a com- 
plete series of results could not be obtained at this time, so the work 
was continued the following season. 

The trees were girdled by removing a strip of bark approxi- 
mately one inch in width from the trunk of the tree, the girdle usually 
being quite close to the ground. Trees were girdled at regular inter- 
vals thruout the spring and early summer and the subsequent effects of 
the girdling noted by determining the depression of the freezing point of 
the saps from time to time. These depressions were determined for 
all parts of the tree, leaves, twigs, trunk, and roots. In the case of 
woody tissues, the cortex only was ground up and pressed. The 
sap was expressed and the freezing point determined as described 
above in the case of the fruit spurs. The following tables present 
the data secured. 

Table 29. — Effect of Girdling Upon the Depression of Trunk Sap 
1 — Bark from below girdle. 2 — Bark from above girdle 



Date of Girdling 




D 


;pression 


on Date Given, 1915 






June 1 


June 19 


July 7 


July 28 


Aug. 18 


Sept. 10 


Oct. 23 


Kov.20 


Check 


1 
2 
1 
2 
1 
2 
1 
2 
1 
2 
1 
2 
1 
2 
1 
2 


0.920 
0.920 
1.320 


0.995 
0.735 
1.160 
0.765 
1.205 
0.785 
1.025 


0.870 
0.820 
1.370 
0.920 
1.470 
0.720 
1.300 
0.800 
1.030 


0.890 
0.790 
1.310 
0.920 
1.290 
0.830 
1.190 
0.780 
1.080 
0.820 
0.910 


0.870 


1.070 


1.360 


1.320 


































Tune 9 




0.660 
1.210 
0.520 
1.250 
0.650 
1.090 
0.810 
1.000 


















July 1 




0.630 
1.860 
0.850 
1.310 
0.910 
1.220 
0.930 
1.130 
















July 15 






0.930 
1.420 
0.750 
1.450 
0.830 
1.550 
0.930 
1.380 


1.290 










1.250 


July 31 








0.700 












1.830 


August 18 










0.820 












1.740 


September 8 












0.890 














1.700 



















40 MISSOURI AGK. EXP. STA. RESEARCH BULLETIN 32 

Table 30. — Effect of Girdling Upon the Depression of Twig Sap 



Date of Girdling 




Depression on 


Date Given, 1915 




June 3 


June 21 | June 24 


July 7 


July 28 


Aug. 18 


Check 


1.240 
1.4S0 


1.200 
1.380 


1.200 


1.090 
1.370 
1.300 
1.250 
1.170 


0.870 
1.050 


1.020 


May 29 

June 9 

July 1 

July 15 

July 31 


1.450 
1.410 








1.090 
1.170 
1.110 


0.870 






1.210 








1.230 










1.150 













Table 31. — Effect of Girdling Upon the Depression of Leaf Sap 



Date of Girdling 






Depression on 


Date Given, 1915 




June 3 


June 21 


July 7 


July 28 


Aug. 18 


Sept. 10 


Oct. 23 


Check 

April 27 
May 29 . 
June 9 

July 1 . 


1.410 
2.050 


1.950 
2.250 
1.970 
2.270 


1.900 
2.420 
2.210 
2.270 

2.140 


1.630 
2.360 
2.710 
2.020 
1.970 
1.940 


1.400 


2.010 


2.570 










1.825 
2.210 
1.860 

1.780 








2.130 
1.970 
1.820 
2.000 




July 15 

July 31 
August 18 .... 
September 8 






2.800 


















2.740 












2.770 

















Table 32. — Effect of Girdling Upon the Depression of Root Sap 



Date of Girdling 






Depression 


on Date 


Given, 1915 




June 21 


July 7 


July 28 


Aug. 19 


Sept. 10 


Nov. 5 


Nov. 22 


Check 

April 27 


0.830 
0.640 
0.680 
0.690 


0.740 
0.720 
0.570 
0.550 
0.670 


0.750 
0.500 
0.610 
0.630 
0.590 
0.640 


0.900 


0.960 


1.120 


1.310 


May 29 










0.800 
0.620 

0.540 
0.700 








July 1 


0.620 
0.975 
0.730 
0.780 






July 15 




0.890 
0.720 

0.700 
0.660 


1.090 


July 31 




0.650 


August 18 








0.790 


September 8.... 










0.940 

















A study of the preceding tables shows rather distinctly the fol- 
lowing features. In the case of sap from the trunk of the tree, the 
girdled trees had the highest concentration above the girdle and the 
lowest below, with the check tree intermediate. These differences 
were discernible almost immediately after the girdle was made, and 
remained consistent. However, there is evidence pointing to the con- 
clusion that these differences grow less as the season advances. When 
it is considered that in many cases the girdled area had been partly 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 



41 



or almost entirely healed over by cambium development, this evidence 
is not surprising. 

Twig sap from girdled trees is slightly more concentrated than 
that from normal trees but the difference is hardly so great as those 
noted above for trunk sap. Leaf sap shows more variation than 
either the twig or trunk sap but in a majority of the determinations 
the leaf sap from the girdled tree possessed the greater supply of 
plant food as evidenced by its lower freezing point. 

Root sap differs from the other portions of the tree by having a 
sap of the lower concentration in the case of girdled trees. 

From the foregoing it is readily seen that the sap of all parts 
above the girdle has an increased sap density, and that of all parts 
below, a decreased sap density, when compared with sap from cor- 
responding parts of similar ungirdled trees. 

Nursery trees were also used for the 1916 work, but these were 
four or five years old, — in fact, they were sufficiently old that some 
had begun to produce a small amount of fruit. The scope was 
broadened so that in addition to the root and trunk sap, leaf sap was 
secured from new growth, both above and below the girdle, and from 
the one-year-old spurs, potential fruiting wood, which the trees had 
developed. The twig sap determinations were made upon sap from 
the new growth both above and below the girdle and also from the 
one-year-old twigs. 

Examinations of the trees had revealed that several specimens 
had been either totally or partly girdled by rabbits the previous win- 
ter (1915-16). It was decided to include these along with the newly 
girdled trees, to see just what effect such injury might have upon 
the plant sap. 

The trees were girdled in a manner similar to that employed 
upon the earlier ones and the determinations made as noted above. 
The results follow : 

Table 33. — Effect of Girdling Upon the Freezing Point 
Depression of trunk sap above the girdle 



Date of Girdling 




Depression on Date Given 


, 1916 




June 12 


June 26 | July 12 


July 24 


Aug. 7 


Aug. 24 


Check 

Partly girdled by rabbits 
1916 - 17 


1.220 
1.430 
1.000 


1.510 

1.340 

1.660 
1.460 


1.085 

1.280 

1.395 
1.110 
1.020 


1.255 

2.025 

1.765 
1.760 
1.245 

1.250 


2.145 

2.255 

2.250 
2.195 
1.675 
1.665 
2.100 


2.695 

1.715 


Entirely girdled by rabbits 
1916 - 17 


1.925 


June 12 

June 26 

July 11 

July 24 


2.720 




2.070 






2.605 








2.240 










1.695 













42 



M 



ISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 



Table 34. — Effect of Girdling Upon the Freezing Point 
Depression of twig sap 



Date of Girdling 






Depression on 


Date Given 




June 12 


June 26 


July 12 


July 24 


Aug. 7 


Aug. 24 


Check — not girdled 

Partly girdled by rabbit 
winter of 1916-17 

Entirely girdled by rabbits 


1 
2 
3 

1 
2 
3 

1 

2 
3 
1 
2 
3 
1 
2 
3 
1 
2 
3 
1 
2 
3 
1 
2 
3 


1.930 
2.590 
2.000 

1.560 
2.500 
2.540 

1.150 
2.270 
2.100 


1.260 

1.510 
1.800 

1.440 
1.650 
2.030 

1.210 
2.110 
1.410 
1.060 
2.230 
2.760 


1.130 
1.605 
1.640 

1.030 
1.475 
1.375 

0.900 
1.425 
1.540 
0.735 
1.240 
1.455 
0.995 
1.475 
1.895 


1.085 
1.480 
2.200 

1.585 
1.945 
2.260 


1.720 
1.780 
2.210 

1.445 
1.890 
2.330 

1.450 
2.125 
1.780 
1.810 
1.965 
2.845 
1.395 
1.585 
2.035 
1.790 
2.170 
3.100 
1.285 
2.365 
2.490 


1.495 
1.900 
2.665 

1.405 
1.745 
2.355 


June 12 


2.315 

1.715 
1.425 
1.515 
2.175 


1.745 
2.370 
1.920 




1.985 






3.430 


June 26 




1.185 






1.735 
1.620 
1.010 
1.655 
1.795 


1.470 








1.520 


Tuly 11 






1.405 










1.610 










2.460 


July 24 








1.300 










1.605 












2.280 












1.195 














1.695 














2.790 

















NOTE: 1 — New growth below the girdle. 2 — New growth above the girdle. 3- 
year old twigs or spurs. 



-One 



These tables may be very briefly summed up by repeating the 
general conclusions reached from the earlier work, which are that 
the parts above the girdle show a greater density, and the parts below, 
a lesser concentration of plant sap, than is found to be the case 
with check trees. The trees girdled by rabbits exhibit a behavior 
very similar to the other girdled trees except that the sap from the 
partly girdled tree is more variable. This is probably to be expected 
since varying amounts of the cambium had been removed from these 
trees. Sap from corresponding parts above and below the girdle on 
the same tree shows the higher concentration, with few exceptions, 
in the parts above the girdle. As a rule, the sap of one-year-old 
twigs has a greater density than sap from twigs representing the 
current year's growth. Leaf sap from these parts stands in the 
same relation as the twig sap. 

That girdling does lead to increased fruitfulness is a matter of 
common knowledge. The foregoing data furnish one definite reason 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 



43 



Table 35. — Effect of Girdling Upon the Freezing Point 
Depression of leaf sap 



Date of Girdling 




Depression on Date Given 




June 12 


June 26 


July 12 


July 24 


Aug. 7 


Aug. 24 


Check — not girdled 1 


2.940 


1.710 


1.915 


2.265 


2.240 


3.010 


2 


2.730 


1.910 


2.360 


2.555 


2.615 


3.570 


3 


2.530 


2.750 


2.275 


2.435 


2.430 


3.540 


Partly girdley by rabbits 














winter of 1916-17 1 


2.230 


2.160 


1.780 


2.310 


2.325 


2.420 


2 


2.580 


2.140 


2.035 


2.675 


2.790 


2.660 


3 


2.870 


2.070 


2.005 


2.505 


2.460 


3.100 


Partly girdled by rabbits 














winter of 1916-17 1 


1.490 


2.020 


1.515 




2.065 


2.370 


2 


3.150 


2.760 


2.390 


2.825 


2.970 


2.985 


3 


2.800 


2.610 


2.215 


3.015 


2.925 


2.945 


June 12 1 




1.610 
2.880 
2.810 




1.970 
2.725 
2.800 


2.545 
2.995 
2.915 


3.440 


2 




2.300 
2.290 


3.820 


3 




3.070 


June 26 1 

2 










2.130 
2.855 
2.880 
2.145 
3.015 
3.175 
1.990 


2.335 






2.545 
2.550 


2.530 
2.445 
1.975 

2.555 
2.705 


3.010 


3 




2.980 


July 11 1 

2 






2.955 








3.655 


3 








3.785 


July 24 1 

2 








2.230 










2.910 
2.820 


3.010 


3 










3.260 










2.560 


2 












3.570 


3 










3.590 



NOTE: 1 — From new growth below the girdle, 
girdle. 3 — From one year old branches or spurs. 



2 — From new growth above the 



Table 36. — Effect of Girdling Upon the Freezing Point 
Depression of root sap 



Date of Girdling 






Depression 


on Date 


Given 




June 12 


June 26 


July 12 


July 24 


Aug. 7 


Aug. 24 




0.940 

0.920 
0.700 


1.240 

1.010 

0.890 
0.910 


1.210 

1.150 

1.073 
0.825 
1.075 


1.420 

1.685 

1.085. 
1.390 
1.080 
1.245 


1.455 

1.500 

1.410 
1.180 
1.250 
1.675 
1.375 


2.085 


Partly girdled by rabbits 
1916-17 


1.540 


Entirely girdled by rabbits 
1916-17 


1.610 


June 12 


2.355 







1.810 


July 11 




1.940 


July 24 








1.315 










1.530 















why this phenomenon occurs, since it is very evident that girdling 
does cause an increased supply of food materials to accumulate in 
the parts above the girdle. It is conceivable that such an accumula- 



44 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 

tion of reserves should result in the formation of a greater number 
of fruit buds. The data also indicate that girdling in early summer 
is likely to be most efficacious in promoting fruit bud formation 
since the greatest differences in concentration are evident if the 
girdling is done at that time. 

This conclusion does not agree altogether with the data secured 
from the fruit spur studies in which it was found that the differ- 
ences in the amount of food reserves present in bearing and non- 
bearing parts were very slight. However, it will be noted that girdl- 
ing, severe as it is, did not cause a marked difference in the con- 
centration of the sap of the outermost parts of the tree. The great- 
est effect is to be observed on the trunk sap but this difference les- 
sens as the distance from the girdle increases. The leaves and twigs 
at the periphery of the tree where the fruit buds are formed do not 
show such great variation. This may furnish an explanation for 
the slight difference found in the case of the bearing and non-bearing 
spurs. It is entirely possible that the reserves which are responsible 
for fruit bud formation are brought from some point beyond the 
spur itself, and hence, data based upon spur sap alone may not indi- 
cate the difference which actually exists in the food supply. 

THE EFFECT OF FERTILIZERS UPON FRUITFULNESS 

The following experiment, begun at the Missouri Experiment 
Station in 1914, was designed to show the specific effects of chemi- 
cal fertilizers, applied either singly or in combination, upon the 
fruitfulness of apples. The results are as yet incomplete, since the trees 
are just beginning to show some of the effects of the fertilizers. It 
is the plan to continue the work for several seasons, but a part of 
the data are of interest in connection with this investigation and for 
that reason are included here. 

The plants used for this work were one-year-old Rome Beauty 
apple trees, budded upon Paradise stock. The trees were very uni- 
form in size and appearance at the time of planting. They were set 
in wooden boxes 18x18 inches at the top, 16x16 inches at the bottom, 
and 16 inches in depth. One-half the number of boxes were filled 
with Missouri River sand and the other half with loess soil. The 
amount of sand used in each case was 75 kilograms, and of soil, 90 
kilograms. Suitable samples showed that the soil contained 13.27 
per cent of moisture while the sand held only 3.42 per cent. 

It was thought that by planting the trees in the boxes, the effect 
of the fertilizers could be more readily distinguished, since there 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 



45 



would not be so many outside factors to be taken into consideration. 
For similar reasons, it was thought advisable to use sand, a medium 
practically free of plant food, on one medium and loess soil, a soil 
type well suited to fruit trees generally, for the other. Both mechani- 
cal and chemical analyses were made of the sand and of the soil. 
These analyses in tabular form follow: 



Table 37. — Chemical Analyses of Loess So t l and Missouri River Sand* 



Material 



Per Cent in 
Loess Soil 



Per Cent in 

Sand 



Water** 

Total Nitrogen .... 
Total Phosphorus 
Total Potassium 



1.740 
.019 
.073 

1.667 



.110 

.oos 

.036 
1.599 



*Analyses furnished by Agricultural Chemistry Department of Missouri Experiment 
Station. 

**ln air-dry material. 

Table 38. — Mechanical Analyses of Loess Soil and Missouri River Sand 



Soil Particles 



Per Cent in 
Loess Soil 



Per Cent in 
Sand 



Fine gravel 

Coarse sand 

Medium sand ... 

Fine sand 

Very fine sand 

Silt 

Clay 



0.00 

0.00 

0.93 

45.79 

33.81 

11.07 

8.42 



6.59 

19.05 

35.33 

35.31 

0.13 

0.00 

3.47 



The fertilizers used have been sodium nitrate, acid phosphate, 
and potassium sulphate, in their common commercial forms. They 
were applied singly and in all possible combinations. Each plot con- 
tained eight trees, four in loess soil and four in sand. A check plot 
received no treatment at all. All fertilizer applications were made in 
the spring just as growth was beginning. The amounts used per 
tree were, sodium nitrate, 15 grams; acid phosphate, 30 grams; and 
potassium sulphate, 30 grams. 

The trees have remained exposed to outside conditions from the 
time of planting, except that during the winter the roots have been 
protected somewhat from the cold by filling the spaces between the 
boxes with sawdust and also covering the boxes with boards. When- 
ever necessary, water has been supplied during summer drouths. 
Figure 3 shows the trees in the second seasons's growth. 

Data have been kept upon a great many different points, but the 
only phases of any particular interest here are (1) the number of 



46 



MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 



potential fruiting parts developed and (2) the actual number of 
fruit buds formed. The number of fruiting parts was determined 
by counting the number of short branches, two inches or less in 
length, that had developed on the various trees, and the number of 
fruit buds by counting the number of blossom clusters that opened. 
These figures are given in Tables 39 and 40. 

Table 39. — Average Number of Potential Fruiting Parts Developed on 
Trees in Fertilizer Experiment 





Medium 


Year 


Fertilizer 










1916 


1917 




Soil 


S3 


64 




Sand 


8 


28 




Soil 
Sand 


9 
12 


21 




17 




Soil 
Sand 


8 
4 


19 




18 




Soil 
Sand 


31 
9 


62 




33 




Soil 
Sand 


49 
2 


52 




35 




Soil 


8 


IS 




Sand 


S 


15 




Soil 


45 


69 




Sand 


6 


22 




Soil 


8 


20 




Sand 


6 


30 



NOTE: N — Sodium Nitrate. K — Potassium Sulphate. P — Acid Phosphate. 



Table 40. — Total Number of Blossom Buds Produced on Trees in Ferti- 
lizer Experiment 



Fertilizer 


Medium 


No. Trees 


Blossom Buds 


in 












1916 1917 


1918 


N 


Soil 
Sand 


2 
4 


7 



45 



22 




83 


K 


Soil 


3 













Sand 


4 











P 


Soil 


3 













Sand 


4 











NK 


Soil 


4 


11 


29 


287 




Sand 


4 


2 


8 


241 


NP 


Soil 


4 


8 


8 


117 




Sand 


4 


1 


27 


139 


KP _ 


Soil 


3 













Sand 


3 











NKP 


Soil* 


4 


37 


124 


306 




Sand 


4 


2 


1 


107 


Check 


Soil 


4 








2 




Sand 


4 





° 1 


6 



NOTE: N— Sodium Nitrate. K— Potassium Sulphate. P— Acid Phosphate. 
*One tree in this lot had become girdled with a label wire and it alone produced 24 
clusters in 1915. 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 47 

From these two tables, it is very evident that the application of 
nitrogen has been a very decisive factor in both the formation of 
fruiting parts and the development of bloom buds. Apparently the 
mediums used needed little or no potassium or phosphorous in this 
connection, for these elements gave really no increase over the check 
when applied either singly or in combination. It is only where the 
nitrogen was added that any effect is noted, this effect being nearly 
as great in the loess soil plots as in the sand plots. 

EFFECT OF THE TILLAGE SYSTEM UPON THE CON- 
CENTRATION OF SAP IN YOUNG APPLE TREES 

That the method of handling the soil and the kinds of plants 
used for intercropping a young orchard have considerable effect upon 
the subsequent bearing and behavior of apple trees is the conclusion 
that must be reached if weight is given the opinions of many grow- 
ers. This phase of orchard management is now receiving consider- 
able attention at the Missouri Experiment Station. Quite an exten- 
sive experiment was begun in 1911. Many of the trees, however, 
were not set until a year or two later. From time to time, it has 
also been necessary to replant because certain trees died. The 
present planting, therefore, consists of trees of different ages. 

fhe problem, primarily, has been to make observations relative 
to the effect of various kinds of intercrops and cover crops and 
methods of soil treatment upon the vigor, size, earliness of bearing, 
and amount of fruit produced upon apple trees set in the loess soil 
on the University Fruit Farm. The planting consisted of several 
commercial varieties but it was so arranged that several trees of 
each variety were .included in each of the tillage plots. 

In arranging the cropping systems, an attempt was made to 
provide various degrees of cultivation ranging from clean cultiva- 
tion with a leguminous cover crop, to a permanent timothy and blue- 
grass sod. In one plot, the ground was kept in a high state of cul- 
tivation up until June each year when a crop of cowpeas or soy- 
beans was planted. A second plot has grown successive crops of 
corn, a third has been planted to red clover in alternate years, a fourth 
has produced successive crops of alfalfa and another has been seeded 
to permanent timothy sod. Thus, it will be observed that two plots are 
cultivated each year, one is plowed in alternate years and the others 
(one planted with a legume and one with a grass) receive no culti- 
vation. (As a matter of fact, it has been necessary to plow and 



48 



M 



ISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 



then reseed the alfalfa plot two or three times on account of blue- 
grass.) 

This project has by no means been carried to its conclusion, for 
the older trees are just now beginning to come into bearing. How- 
ever, the following data concerning the freezing point depression of 
twig and leaf sap are of interest in connection with the present prob- 
lem and for that reason are presented here. 

Table 41. Effect of the Tillage Method Upon Depression of Twig Sap 

of Apple Trees 





Variety 


Depressions in the Various Plots 


Date 


Timothy 


Alfalfa Clover 


Corn Cowpeas 


Mar 11 1916 


Jonathan 
Benoni 
Delicious 
Jonathan 
King David 
Ben Davis 
King David 
Rome 


2.32S 
2.350 
1.510 
1.760 
1.822 
1.543 
1.439 
1.407 


2.435 
2.395 

1.675 
1.695 
1.973 
1.687 
1.517 
1.453 


2.275 
1.985 
1.655 
1.655 
1.931 
1.604 
1.482 
1.426 


2.230 
1.980 
1.525 
1.765 
1.716 
1.454 
1.339 
1.349 


2.195 


\pr 10 1917 


2.220 
1.675 
1.685 


Nov 6 1917* 


1.755 


Mar. 22, 1918* 


1.398 

1.215 
1.361 



*These determinations were made by A. J. Winkler. 



Table 42. — Effect of the Tillage Method Upon the Depression of Leaf 

Sap of Apple Trees 





Variety 


Depressions ir 


the Various Plots 




Date 


Timothy 


Alfalfa 


Clover 


Corn 


Cowpeas 


July 5, 1916 


Jonathan 


3.440 




2.790 


3.540 


3.640 


3 160 




2.790 


2.960 


2.290 




Delicious 


3.400 


2.830 


3.460 


3.500 


2.490 


July 19, 1916 


Jonathan 


2.725 


3.070 


2.553 


2.290 


2.195 




Delicious 


2.065 


2.265 


2.140 


2.280 


1.995 




Ben Davis 


2.770 


2.305 


2.030 


2.310 


2.115 




King David 


2.470 


2.755 


2.925 


2.530 


2.405 


Aug. 4, 1916 


Jonathan 


2.285 


2.520 


2.200 


2.465 


2.570 




Delicious 


2.180 


2.245 


2.485 


2.310 


2.305 




Ben Davis 


2.260 


2.505 


2.385 


2.220 


2.180 




King David 


2.430 


2.455 


2.565 


2.500 


2.875 


Aug. 16, 1916 


Jonathan 


2.255 


2.190 


2.305 


2.330 


2.230 




Delicious 


1.935 


2.040 


2.125 


1.975 


1.875 




Ben Davis 


1.830 


2.010 


1.960 


1.905 


1.890 




King David 


2.210 


2.440 


2.615 


2.500 


2.140 



Table 41 shows very conclusively that the tillage method does 
materially affect the sap density of the twigs of apple trees. Con- 
trary to what might have been expected, trees from the alfalfa plot 
show a greater depression of twig sap than trees from the timothy 
plot. As a general thing, there is not much difference between trees 




Fig. 5. — Jonathan apple tree showing effects of severe pruning. Note the 
large amount of watersprout growth. (Compare with Figure 6) 




Fig 6. — Jonathan apple tree showing development of a large number of 
fruiting parts. (Compare with Figure 5, a tree of the same age but 
pruned more severely) 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 49 

growing in clover sod and those intercropped with corn. These 
stand next to timothy in density and first above the trees in the 
cowpea plot. In the latter case, the concentration is least of all. 

From these data, it would seem logical to conclude that the trees 
growing in timothy or alfalfa should be the ones to come into bearing 
earliest, a conclusion also supported by general observations. How- 
ever, it must be stated that the trees in the more intensively culti- 
vated areas are considerably larger at the present time and hence, in 
this way may be able to overcome the advantage that the other trees 
may now possess. 

The figures representing the depression of leaf sap from trees 
growing in the various plots present such a wide range of variation 
that no safe conclusion can be drawn. 

EFFECT OF THE PRUNING SYSTEM UPON THE 
FORMATION OF FRUITING PARTS 

That pruning does have a very marked influence upon the 
fruiting habit of the tree has long been a matter of common obser- 
vation. Dormant pruning in most instances has tended to promote 
wood growth and to decrease fruitfulness. Even different amounts 
of pruning done at the same time show considerable variation in 
their effects. 

That the system of pruning may likewise be influential in caus- 
ing the formation of fruit spurs is also nicely shown by the follow- 
ing figures compiled from data collected under another project. A 
pruning experiment was begun in 1914 upon 64 one-year-old Delicious 
apple trees with the object of determining the relative influence of 
different pruning systems (particularly high heads vs. low heads) 
upon the size, the character of growth, and the fruiting age of ap- 
ple trees. The experiment is incomplete, yet the following table is 
interesting in connection with the present problem. 

The trees were very uniform in size and were treated in ex- 
actly the same manner except one series was forced to form the 
head at a height of about two feet and the other at five to six feet. 
The accompanying photograph (Fig. 4) indicates the appearance of 
the trees after their first season's growth. 

From the beginning it has been very noticeable that the low- 
headed trees make by far the greater amount of twig length growth 
and at the same time form a much larger number of branches. Dur- 
ing the season of 1917, it was observed that the low-headed trees 
were forming a great many very short branches which made only a 



50 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 

limited growth, usually two inches or less, and then formed a termi- 
nal bud. Since this is the usual history of the formation of fruit- 
ing parts, it has been assumed that these were potential fruit spurs. 
While a large number of such branches probably would never develop 
into fruit spurs under normal conditions, yet it is likely that the 
relative number in the two sets of trees would be maintained. A 
record of the number of these short branches as well as the number 
of longer twigs was taken in the fall of 1917. The figures are 
given in Table 43. 

Table 43. — Average Number of Twigs and Fruit Spurs on High- and Low- 
Headed Apple Trees 



No. of Twigs 



No. of Spurs 



High-headed 35.5 

Low-headed 62.8 



14.9 
34.1 



From the foregoing it may be clearly seen that the system of 
pruning used has a very marked influence upon the number of poten- 
tial fruiting parts formed in the early life of the tree, the low headed 
trees forming more than double the number of short branches or 
spurs found on the high-headed trees. 

EFFECT OF ETHERIZATION UPON THE SAP DENSITY 
OF APPLE TREE FRUIT SPURS AND LEAVES 

Etherization has proven to be a very effective stimulant upon 
the enzyme activity of detached parts of woody tissues. Howard 6 * 
has made extensive experiments along this line. Since this treat- 
ment does have a marked effect upon the availability of the food 
supply, the thought has come that perhaps etherization of the entire 
tree at various seasons of the year might have some effect upon the 
amount of available food and thus influence the number of fruit 
buds formed for the following season. For the above reason the 
following experiment has been designed and carried out. 

The effect upon the food supply was measured by the concen- 
tration of the sap from the treated as compared with the untreated 
trees. While they plainly do not justify any definite conclusions, 
yet the results are submitted below. 

A number of Jonathan apple trees were available for this work. 
They were five or six years old, just at the point where fruitfulness 
normally begins. They were growing in the clay loam soil of the 
Experiment Station grounds. 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 



51 



Twelve trees were selected for etherization and a different one 
was etherized each month, beginning December, 1914, and continuing 
until November, 1915. For this exposure the trees were enclosed 
in a galvanized iron can and all joints tightly sealed. Ether was then 
introduced in sufficient quantity to have 0.5 cc. per liter of air 
space. A little injury to the leaves and new growth resulted from 
the May and June treatments. It was undoubtedly due to exces- 
sive temperatures inside the can at that time. Even tho an at- 
tempt was made to keep the temperature down by shading the can, 
yet it sometimes reached a fairly high point during the summer 
months. It is interesting to note that the trees treated in October 
began to show bud growth, especially near the ends of the main 
branches, early in November. 

From time to time sap samples were secured from spurs and 
leaves on both etherized and unetherized trees. The results secured 
are given in Tables 44 and 45. 



Table 44. — Depression of Spur Sap from Et 


tIERIZED 


and Unetherized Trees 




Depression 




Treated Untreated 


June 1, 1915 

June 12, 1915 


1.630 
1.305 


1.580 
1 345 








Table 45. — Depression of Leaf Sap from Etherized and Unetherized Trees 


Depression on Date Given 


! July 16, 1915 June 17, 1916 

i 1 


June 30, 1916 1 July 17, 1916 



December 12, 1914... 

January 12, 1915 

February 20, 1915 

March 12, 1915 

April 12, 1915 

May 13, 1915 

June 12, 1916 

July 13, 1915 

August 10, 1915 

September 12, 1915. 

October 14, 1915 

November 15, 1915.... 
Check 



1.580 
1.530 
1.560 
1.600 
1.630 
1.590 
1.610 
1.660 




2.790 
2.280 
2.280 
2.040 
1.840 
1.730 
2.200 
2.430 
2.000 
1.760 
1.970 
2.280 
2.480 



1.760 
1.750 
1.750 
2.210 
2.180 
2.030 
1.680 
1.680 
1.590 
1.720 
1.760 
1.730 
1.620 



1.710 
1.750 
1.750 
1.910 
1.810 
2.030 
1.640 
1.730 
1.690 
1.740 
2.060 
1.910 
1.950 



The small supply of leaves and spurs on the trees prevented a 
large number of determinations and then, too, the work had to be 
discontinued after the first series. The results probably do not 



52 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 

justify conclusions. It does seem, however, that ether has little effect 
upon the sap concentration of fruit spurs. The sap of the leaves ap- 
parently was affected by such treatment, but, as is seen by the later 
determinations, this effect does not carry over to the next year. The 
effect seems to be immediate. With the higher concentration of the 
leaf sap which comes in July because of etherization, the hypothesis 
might be advanced, that with a greater amount of food available a 
larger number of fruit buds might be formed. No supporting data, 
however, are furnished. 

SUMMARY AND CONCLUSIONS 

Missouri apple yields tend to rotate in three-year cycles, the 
sizes of the crops produced showing the following order: heavy, 
light, medium, heavy, etc. 

A five-year study of the behavior of individual apple fruit 
spurs of six commercial varieties, as contrasted with previous opin- 
ions based upon casual observation of the entire tree or entire 
orchard, leads to the following conclusions : 

Jonathan, Grimes and Winesap are able to develop a fairly high 
percentage of blooms each year, while Rome, York and Gano, pro- 
duce an exceedingly high percentage of blooms one season and a 
very low one the next. 

The varieties used show remarkable uniformity with respect to 
the percentage of the individual fruit spurs which alternate, that is, 
bloom only once in two years. 

Jonathan and Winesap are able to develop blossoms in succes- 
sive seasons on the same spur in a much greater proportion than the 
other varieties observed. 

The soil in which a tree is growing has little effect, apparently, 
upon the performance of the individual spurs, with respect to alter- 
nation. 

The fruitful year of certain alternating sorts may be changed 
by a removal of the blossoms thru either accident or design. 

The age of the spur systems of the various varieties is practically 
the same, ranging usually from two to eight years, three to six or 
seven years being apparently the most effective fruiting age. 

Sap from bearing spurs has a slightly higher concentration 
(lower freezing point) during a considerable portion of the year than 
sap from non-bearing spurs. The depression of the freezing point, 
however, gives no indication of the amount of starch which may be 
present. 



SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 53 

A marked decrease in the sap concentration of both bearing and 
non-bearing spurs occurs in late June or early July. 

Leaf sap from bearing and non-bearing spurs shows considerable 
variation in concentration. 

The number of fruits on a spur affects the concentration of 
neither spur nor leaf sap. 

Sugar and starch are present in slightly greater amounts in the 
bearing spur than in the non-bearing one. (Determinations made by 
chemical methods.) 

Bearing spurs have a smaller total leaf area than non-bearing 
spurs, the difference being due to the number of leaves developed 
rather than the size of the individual leaves. 

Experiments in girdling nursery apple trees gave the following 
results : 

Girdling, regardless of the season, caused an increased concen- 
tration of sap in the parts above the girdle and a decreased concen- 
tration in the parts below. (Determinations made by freezing-point 
method. ) 

Girdling produced its most marked effect in the parts nearest 
the girdle, the effect being lessened as the distance from the girdle 
increased. 

Fertilizer experiments with dwarf Rome apple trees planted in 
boxes of sand or soil showed that effects upon (1) the size of the 
tree, (2) the development of its fruiting wood, and (3) the produc- 
tion of blossoms, could be attributed only to the use of nitrogen. 
Potash and phosphorus applied either singly or in combinations had 
no apparent effects. 

Tillage experiments showed that trees growing in a permanent 
sod of either a grass or a legume had a higher concentration of twig 
sap than trees growing in plots planted with either annual or biennial 
cultivated crops. 

Trees headed at five or six feet did not produce so many short 
branches — potential fruiting wood— during the first three years in the 
orchard, as trees headed at two feet. 

Etherization of young Jonathan apple trees had little effect 
upon the concentration of either twig or leaf sap, and the small 
differences observed seemed to be only temporary. 



54 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32 

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BIOGRAPHY 

I, Cleo Claude Wiggans, was born on a farm near Princeton, Mercer 
County, Missouri, on October 20, 1889. I attended various country schools 
and then entered Princeton High School in 1904, graduating therefrom four 
years later. Entering the College of Agriculture in September, 1908, I was 
able to complete the requirements for the degree, Bachelor of Science in Agri- 
culture, in three and one-half years. I held the position of Student Assistant 
in Horticulture in 1910-1911 and in 1911-1912. I entered the Graduate School 
of the University of Missouri in February, 1912. During the following 
school year I held a Research Fellowship in Horticulture at the same institu- 
tion, and was granted the Master of Arts in June, 1913. 

I was then appointed Assistant in Horticulture in the University of Mis- 
souri, which position I held for one year. I was then advanced in rank to 
Instructor in Horticulture, a position which I am holding at the present time. 



LIBRARY OF CONGRESS 




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